Flex Pitch appears to be distorting audio

[Dave K]

Hi folks, I need your help.

I'm dealing with a pernicious audio distortion issue on my piano track. I feel like sometimes it sounds fine; other times I hear pretty clear distortion. A friend of mine heard it, too, when I bounced as .aif. 

I'm quite certain my signal never clipped anywhere, and that the recording was pristine originally. But this was very challenging to record (video, etc), so I don't want to redo it. 

But then I noticed something. It seems like if I am in Flex Time mode, things sound better. But when I switch back to Flex Pitch mode, the distortion comes back. I have definitely made some Flex Time edits on this track. As for Flex Pitch, I did do that one waveform copy/paste I discussed in another thread, to compensate for a weak note, and then I edited its pitch with Flex Pitch. That should be the extent of my Flex Pitch work on this track, and that note is somewhere else, not where the distortion is. 

How should I proceed to fix or even track down this issue? I really don't want to lose all my edits, but I'm not even sure how to go back in time on this track or whether that will even help? 

Thanks in advance! I'm so close to having a final mix, and this is a show-stopper!

____

Here's a link to the project, with the Piano track Soloed and the Markers surrounding two chords. When Flex Pitch is off, you can hear it sounds pretty good. But in Flex Pitch, it's distorted. You can see from the separate region that I already tried copy/paste of the waveform from somewhere else over that second chord to clean it up, thinking the original recording may have been bad. But I think even that replaced chord sounds bad if I'm in Flex Pitch mode. (There are other parts of the piano track that sound distorted; this section was just selected as an example).

Logic Project: https://www.dropbox.com/scl/fo/4rrutszxn91cn3cf8jiqh/h?rlkey=mtaz1cn7h78o8rji1f5lmed2o&dl=0

 

Edited March 2 by Dave K

[Atlas007]

Flex pitch doesn’t work well in polyphonic material. Also monophonic audio material shouldn’t be processed (no Fx such as reverb, etc).

Perhaps trying different Flex pitch algorithms might yield better results? 

Some times decreasing the number of flex markers could also help?

Perhaps bouncing-in-place the time-flexed material before trying to edit with flex pitch might prevent issues.

To go back to previous versions of your project, you could check in your project’s backups, providing those have been created, as defined in your Project Handling Settings (Auto Backup option).

hth

 

[sunbrother]

I use “selection based processing” for small fixes of stuff like this.

[Dave K]

12 hours ago, sunbrother said:

I use “selection based processing”

Thanks so much for this suggestion. I'm new to "selection based processing" and it looks useful. But it looks like it's mainly for applying an effect / plugin to just a portion of a track instead of the whole thing?  Maybe it's an alternative to having to use automation to apply an effect to just a section of the recording?

But how do you see it helping me here? Logic has done something to distort my audio which was originally pristine...

[Dave K]

Thanks so much for your thoughtful reply. Lots of interesting comments here.

22 hours ago, Atlas007 said:

Flex pitch doesn’t work well in polyphonic material.

You're right that this piano track is polyphonic. However, the ONE note where I modified the pitch using Flex Pitch was a single piano note, not a chord. And I recall that one sounding flawless when I was done with it. The audio distortion is somewhere else in the performance. Do you think flexing that one note could have caused problems elsewhere in the track?

22 hours ago, Atlas007 said:

Also monophonic audio material shouldn’t be processed (no Fx such as reverb, etc).

That's an interesting comment. So, no reverb on something like a sax solo?

22 hours ago, Atlas007 said:

Perhaps trying different Flex pitch algorithms might yield better results? 

That sounds intriguing. I know Flex Time has various algorithms, but where can I access the other Flex Pitch algorithms?

22 hours ago, Atlas007 said:

Some times decreasing the number of flex markers could also help?

I think I read this somewhere. I guess I could go through and delete all the ones I'm not using. But wouldn't it be a bug for Logic to introduce distortion because of the number of flex markers? Note that I'm not talking about real-time playback. Even bouncing the mix to a .wav file creates distortion, so Logic can't blame it on my CPU limitations since it's free to take as much time as it needs...

22 hours ago, Atlas007 said:

Perhaps bouncing-in-place the time-flexed material before trying to edit with flex pitch might prevent issues.

I may have to figure out how to try this. I guess there's no way to undo specific waveform or Flex Pitch edits?

22 hours ago, Atlas007 said:

To go back to previous versions of your project,

Thanks, but I definitely don't want to roll back the entire project. I've made countless tweaks to this mix. Going to a backup would also delete entire tracks that hadn't been recorded yet. I believe all my edits have been in the Audio Track Editor, which is supposed to be "non-destructive" (as opposed to the Audio File Editor). I feel stupid, but I can't find in the GUI or the manual how to undo Flex or Waveform edits, even though they're all done in the Audio. Track Editor. And like I said, I'd really like to not have to go all the way back to my original piano track; if I could just reset Flex Pitch edits and leave all my Flex Time and/or Waveform edits, that would save me a ton of backtracking...

Thanks in advance!!

DK

 

[Atlas007]

1 hour ago, Dave K said:

That sounds intriguing. I know Flex Time has various algorithms, but where can I access the other Flex Pitch algorithms?

My bad… I got confused, I should have written flex timeinstead of flex pitch.

1 hour ago, Dave K said:

The audio distortion is somewhere else in the performance. Do you think flexing that one note could have caused problems elsewhere in the track?

The thing is that it is pretty hard to remotely figure out such an issue, just like that from a written description. The possible causes here are countless. 

One of the possibilities could be that your project got somehow corrupted; another could be the use of a plugin that is defective or in demo version or not having been registered properly or re-registered. The issues could be related to the soundcard or its driver. Etc…

Posting you project could perhaps find someone to verify same, providing that his/her system configuration is similar to yours…

In regard of reverting to backups, since a backup is created every time a Save command is issued, you might not have to go back too far. That of course depends on your workflow (how often you save your project while working on it).

Just a thought: if the distorsion always occur at the same place, I would try to isolate and mute that part and copy/move it to another track where you could try correcting it. Doing same might also help troubleshooting the source of your issue.

Edited March 3 by Atlas007

[sunbrother]

3 hours ago, Dave K said:

But how do you see it helping me here?

You can use selection based processing to pitch shift individual notes with your highest quality pitch shifter effect.

I have personally found with Flex Pitch and Flex Time it pays to work with as little of the audio as possible and immediately bounce it once it sounds good to my ear. Sometimes that means making multiple tracks with varying methods, bouncing, and then moving the bounced material to a single track with no flex modes enabled. Otherwise you get stuff like this distortion etc happening after a while. Or your edits getting messed up. I don’t know why it happens, it just does.

Edited March 3 by sunbrother

[Atlas007]

2 minutes ago, sunbrother said:

I have personally found with Flex Pitch and Flex Time it pays to work with as little of the audio as possible and immediately bounce it once it sounds good to my ear. Sometimes that means making multiple tracks with varying methods, bouncing, and then moving the bounced material to a single track with no flex modes enabled. Otherwise you get stuff like this distortion etc happening after a while. Or your edits getting messed up. I don’t know why it happens, it just does.

+1

[Dave K]

3 hours ago, Atlas007 said:

Posting you project could perhaps find someone to verify same, providing that his/her system configuration is similar to yours…

Thanks again for the reply! I did post a link to the project above... Try it! 🙂

[Atlas007]

Just listened to it.

I don't have the RX10 plugin, nor the movie that goes with your project.

Upon loading the project the freezing of the tracks started automatically.

Anyhow, I don't hear any distortion in the selected cycle area.

Could you post a sound file here so I could hear the distortion you are talking about.

BTW, that Girl from Ipanema version project sounds pretty good!

[Dave K]

20 hours ago, sunbrother said:

You can use selection based processing to pitch shift individual notes with your highest quality pitch shifter effect.

Okay, that's a fascinating idea. Built-in, I found:

1) AUPitch - this doesn't have support for shifting by semi-tones

2) Pitch Shifter - This seems like it "should" work. I tried selection-based processing to move one vocal note to another pitch, and the result sounds really unnatural and non-human, even if the pitch is definitely shifted to where I requested. I had it on the "Vocal" algorithm. In contrast, the Flex Pitch adjustments sound fantastic. You can't even tell that recording alterations have been made.

Have you found some type of pitch shifter effect that creates authentic sounding pitch changes on vocals?

21 hours ago, sunbrother said:

I have personally found with Flex Pitch and Flex Time it pays to work with as little of the audio as possible and immediately bounce it once it sounds good to my ear.

Sounds like this is the consensus. Too bad, because this audio corruption sounds like a bug Apple should fix. Maybe I'll report it. 

I have avoided bouncing so far, because it's destructive, and I'm not confident enough of what I'm doing that I'm sure I won't want/need to go back to the original recordings, or how easy it is to get back to them. I saw that bouncing regions in place can leave the old ones muted underneath, which seems cool. But then I noticed that as soon as I move around the one on top, it deletes whatever's underneath, so I'm not going that route 😅

Maybe the safe thing to make sure I can always go back to my original recording is this workflow:

1) record into track X

2) use the Option-Drag feature to duplicate the entire track with audio to a new track Y

3) mute X

4) do all my edits on Y (Flex, effects, automation, waveform...)

5) if Logic screws up Y, I start over with X (I don't lose work on other tracks like I would if I rolled back to a backup file)

6) if all goes well, bounce Y in place. Or if I'm paranoid, repeat (2) before bouncing.

Would this be considered a good workflow?

Thanks again!

DK

[Dave K]

13 hours ago, Atlas007 said:

Anyhow, I don't hear any distortion in the selected cycle area.

Could you post a sound file here so I could hear the distortion you are talking about.

First of all, thanks for the compliment 🙂

Okay, so! Here is a greatly-slimmed-down (95 MB) version of the project with just the piano track, and the markers set to just the first chord. No dependency issues that should show up when you open it:

Logic Project, Piano Track Only: https://www.dropbox.com/scl/fo/5kmidltdnr6fp8yymvqga/h?rlkey=md6gnugcmxzfg9c4udwi90c64&dl=0

And here are a pair of audio exports:

1) Flex OFF:

 

2) Flex ON: 

 

Hopefully you'll be able to hear how bad this is!

DK

 

 

[sunbrother]

1 hour ago, Dave K said:

Okay, that's a fascinating idea. Built-in, I found:

1) AUPitch - this doesn't have support for shifting by semi-tones

2) Pitch Shifter - This seems like it "should" work. I tried selection-based processing to move one vocal note to another pitch, and the result sounds really unnatural and non-human, even if the pitch is definitely shifted to where I requested. I had it on the "Vocal" algorithm. In contrast, the Flex Pitch adjustments sound fantastic. You can't even tell that recording alterations have been made.

Have you found some type of pitch shifter effect that creates authentic sounding pitch changes on vocals?

Sounds like this is the consensus. Too bad, because this audio corruption sounds like a bug Apple should fix. Maybe I'll report it. 

I have avoided bouncing so far, because it's destructive, and I'm not confident enough of what I'm doing that I'm sure I won't want/need to go back to the original recordings, or how easy it is to get back to them. I saw that bouncing regions in place can leave the old ones muted underneath, which seems cool. But then I noticed that as soon as I move around the one on top, it deletes whatever's underneath, so I'm not going that route 😅

Maybe the safe thing to make sure I can always go back to my original recording is this workflow:

1) record into track X

2) use the Option-Drag feature to duplicate the entire track with audio to a new track Y

3) mute X

4) do all my edits on Y (Flex, effects, automation, waveform...)

5) if Logic screws up Y, I start over with X (I don't lose work on other tracks like I would if I rolled back to a backup file)

6) if all goes well, bounce Y in place. Or if I'm paranoid, repeat (2) before bouncing.

Would this be considered a good workflow?

Thanks again!

DK

I think Logic’s Pitch Correction plugin is a better choice. The other built in pitch shifters aren’t great for vocals but can be good for instruments sometimes. I prefer Waves Soundshifter when doing the Selection Based Processing approach.

what you’re suggesting for a workflow is OK, but I prefer to use Track Alternatives so I don’t end up with mess of tracks.

track 1: recorded audio

track 2: flex time

track 3: flex pitch

Select track one, use the Rename Track alternative command and call it “original”, use the Duplicate Track Alternative key command, rename it to “comp”.

Do as many edits as possible without time stretching wherever I can (split, move, crossfade)

drag pieces to 2 and 3, edit them with flex, bounce or select a Marquee and hit CMD J

Copy the new region, select track one, hit the key command for create new alternative, use a key command for Paste at Original position, select original alternative (my “comp” track basically, as opposed to Logic’s take folder comp feature) use key command for paste at original position.

the reason I do it this way is so if Flex Time messed up a small moment of a piece in the middle of the section, it’s easier to fix it with the original audio if I can see where it needs to go

it also helps avoid any wasted time from delays where I’m trying to “preserve” pre-edit audio and constantly juggling tracks. It is preserved, so I can just move quickly and then at the end re-do a couple small spots as needed.

hopefully that makes sense. 

Edited March 4 by sunbrother

[Atlas007]

2 hours ago, Dave K said:

Maybe the safe thing to make sure I can always go back to my original recording is this workflow:

1) record into track X

2) use the Option-Drag feature to duplicate the entire track with audio to a new track Y

3) mute X

4) do all my edits on Y (Flex, effects, automation, waveform...)

5) if Logic screws up Y, I start over with X (I don't lose work on other tracks like I would if I rolled back to a backup file)

6) if all goes well, bounce Y in place. Or if I'm paranoid, repeat (2) before bouncing.

Would this be considered a good workflow?

As long that works for you, that’s all that count…

As previously hinted by @sunbrother, that is pretty much what is happening (under the hood, in a more elegant way) when you use Track Alternatives…

[Dave K]

4 hours ago, sunbrother said:

I think Logic’s Pitch Correction plugin is a better choice.

Okay, that makes sense. I have played with that at some length, and it certainly sounds natural. If I'm just editing a few individual notes, though, I think Flex Pitch might be less hassle. I'm just gonna have to keep a close eye out for audio corruption.

4 hours ago, sunbrother said:

I prefer to use Track Alternatives so I don’t end up with mess of tracks

Okay, damn, Track Alternatives seems perfect for what I'm trying to do. After I read this, I spent all evening reading up on and experimenting with the feature. It's perfect. It keeps all by save-points tidy and organized with useful names so I have a clean, documented history of what I changed. I'll probably also number them in sequence since they are going to be cumulative. 

4 hours ago, sunbrother said:

use the Duplicate Track Alternative key command, rename it to “comp”.

Do as many edits as possible without time stretching

Trying to follow here. These edits are on your "comp" alternative? But then you have another comp track later called "original alternative"?

Next question: 

4 hours ago, sunbrother said:

the reason I do it this way is so if Flex Time messed up a small moment of a piece in the middle of the section, it’s easier to fix it with the original audio if I can see where it needs to go

I think I get this, but then why do you Join them all together? Wouldn't you be able to go back and see the pieces you edited better, if needed, if you left the pieces/regions intact?

Also, if you do Flex Time and Flex Pitch edits in parallel on separate track alternatives, how will you merge them back into a single track? Don't you have to do one first, copy the track alternative, and then do the second on top?

Your workflow sounds very effective, but I want to understand it 🙂

Thanks in advance!!

 

[Atlas007]

8 hours ago, Dave K said:

First of all, thanks for the compliment 🙂

Okay, so! Here is a greatly-slimmed-down (95 MB) version of the project with just the piano track, and the markers set to just the first chord. No dependency issues that should show up when you open it:

Logic Project, Piano Track Only: https://www.dropbox.com/scl/fo/5kmidltdnr6fp8yymvqga/h?rlkey=md6gnugcmxzfg9c4udwi90c64&dl=0

And here are a pair of audio exports:

1) Flex OFF:

2) Flex ON: 

Hopefully you'll be able to hear how bad this is!

DK

 

Ok.

I hear what is happening. Both here and from your latest project upload to DropBox (piano distortion- take 2.logicx).

As mentioned previously, that is due to Flex Pitch being unable to deal with polyphonic material.

Check in the "piano distortion- take 3.zip" project what I did to correct same, download that project using this DropBox link.

[sunbrother]

11 hours ago, Dave K said:

These edits are on your "comp" alternative? But then you have another comp track later called "original alternative"?

The "Comp" is my final track.

The "Original" is the original audio, in case I need to go back to grab a piece of it.

11 hours ago, Dave K said:

but then why do you Join them all together? Wouldn't you be able to go back and see the pieces you edited better, if needed, if you left the pieces/regions intact?

Because Joining a Marquee selection commits Flex edits.

11 hours ago, Dave K said:

Also, if you do Flex Time and Flex Pitch edits in parallel on separate track alternatives, how will you merge them back into a single track? Don't you have to do one first, copy the track alternative, and then do the second on top?

Perhaps the GIF below will make sense of all this. I do this all by using the following commands and a "Flex Edits" alternative on the final track:

Control + Alt/Option + A shows all the Track Alternatives for a track.

Clicking the arrow on an alternative makes it the primary alternative. There might be a key command for this.

Option + Left Click on a track control panel selects a track without taking focus off of regions.

CTRL+SHIFT+T moves all the selected regions to the focused track.

The attached GIF shows most of this. I tend to work with small sections of the performance because I find it is much faster and less artifact/error/distortion prone than thinking "I might as well correct everything because I can." A lot of the distortion comes from quantity of edits and splitting regions that have been Flex edited. The latter is much more likely to come up if you're trying to Flex edit a whole song in one go.

If at any point I hear a bad artifact or I did a Flex Edit in a way that I later want to change, I can always utilize the "Original" alternative in some way to solve it. I find this much faster than thinking "I might as well leave it on a separate track until I'm completely finished"

 

Edited March 5 by sunbrother

[Dave K]

12 hours ago, Atlas007 said:

As mentioned previously, that is due to Flex Pitch being unable to deal with polyphonic material.

Thanks so much for the follow up. I think I get what you're saying. So even though the ONE Flex Pitch edit I did to the piano track was to a single note (not a chord; monophonic), the fact that the track as a whole was polyphonic affected Logic's algorithm and caused it to distort audio that hadn't been pitch-adjusted at all? I wonder if the portions that were distorted by Flex Pitch were the ones that were time-adjusted by Flex Time.....

12 hours ago, Atlas007 said:

Check in the "piano distortion- take 3.zip" project what I did to correct same, download that project using this DropBox link.

Very cool. So I think what you're showing me is that your solution is to split the track into two, and perform Flex Pitch edits on #1, and move select regions for Flex Time edits to #2. Am I following?

By the way, notice that you can still hear distortion such as on measures 98-102. The distortion goes away if you disable Flex Pitch on that track. So is your proposal to cut out those regions and move them to Track #2 where Flex Pitch will stay off?

[sunbrother]

58 minutes ago, Dave K said:

the fact that the track as a whole was polyphonic affected Logic's algorithm and caused it to distort audio that hadn't been pitch-adjusted at all

This is the reality of Logic’s Flex methods and has been for ages. Hence why I try to use entirely new tracks for any flexing and only do the piece I need to before bouncing it and dragging it back to the main track. 

[Dave K]

2 hours ago, sunbrother said:

Hence why I try to use entirely new tracks for any flexing and only do the piece I need to before bouncing it and dragging it back to the main track

Very helpful tip for a very annoying issue. It appears that's what @Atlas007 is doing as well. It's too bad you can't enable Flex on just a Region instead of a whole Track, eh? Seems like it would simplify workflow a lot.

[Dave K]

11 hours ago, sunbrother said:

Perhaps the GIF below will make sense of all this.

First of all, thanks a TON!

Okay, I played your GIF a frame at a time and reread your posts a ton of times, and I think I'm getting what you're saying and it almost all makes sense. A couple follow up questions:

1) You talked about Track Alternatives, but I see that FLEX PITCH and FLEX TIME are separate tracks entirely. Why not keep them organized as Track Alternatives like the others? Is it because Flex can't be individually enabled on just one Track Alternative, and so enabling it on the entire Track puts the whole Track at risk? And so, after you harvest the edits into "Flex Edits", you just discard the FLEX TIME and FLEX PITCH tracks entirely? If so, I get it.

2) If you have to both Flex Time and Pitch the SAME region, do you just work in series and do the time first and then copy it to the Pitch track and do the pitch work there second?

Thanks again in advance!

DK

[sunbrother]

2 hours ago, Dave K said:

so, after you harvest the edits into "Flex Edits", you just discard the FLEX TIME and FLEX PITCH tracks entirely? If so, I get it.

That’s right.

2 hours ago, Dave K said:

2) If you have to both Flex Time and Pitch the SAME region, do you just work in series and do the time first and then copy it to the Pitch track and do the pitch work there second?

I try not to do both in series because of artifacts adding up. You can timestretch within Flex Pitch. It works well on vocals, at least. There are a couple note selection bugs but it’s better than it sounding bad.

Ultimately, if I needed both I would use Melodyne or Auto Tune Pro graph mode. But if it’s one or two notes I use Flex Pitch because it’s faster. Although I use Selection Based Processing to add some highs back afterwards:

 

[polanoid]

9 hours ago, Dave K said:

It's too bad you can't enable Flex on just a Region instead of a whole Track, eh?

Erm, you can? Just set this checkbox as desired in the Region Inspector:

[polanoid]

On 3/3/2024 at 10:46 PM, Dave K said:

However, the ONE note where I modified the pitch using Flex Pitch was a single piano note, not a chord.

On 3/4/2024 at 11:04 PM, Dave K said:

And here are a pair of audio exports:

1) Flex OFF:

2) Flex ON: 

 

That's not monophonic!? 

 

Edited March 6 by polanoid

[Dave K]

7 hours ago, polanoid said:

That's not monophonic!?

Exactly. That's what I was saying, and why I was surprised Flex had trouble with it. But you'll see in this thread that people clarified that because the piano track as a whole was polyphonic, and FlexTime/Poly has trouble getting that material right, it garbled the audio. So various best-practices were suggested as alternatives. I'm still compiling that list 🙂

[polanoid]

5 minutes ago, Dave K said:

That's what I was saying

Well actually you were saying "You're right that this piano track is polyphonic. However, the ONE note where I modified the pitch using Flex Pitch was a single piano note, not a chord"

[sunbrother]

8 hours ago, polanoid said:

Erm, you can? Just set this checkbox as desired in the Region Inspector:

Technically, yes, but that forces the track's Flex mode into Automatic. In my experience, this approach causes some problems. I do this for some loops and samples because it's fast but if I have a long recorded performance I am trying to correct a separate track is much more problem-free.

[Dave K]

8 hours ago, polanoid said:

Erm, you can? Just set this checkbox as desired in the Region Inspector:

Yea, I'm not clear on how "Flex and Follow" works. The manual only mentions Flex Time, not Pitch:

Quote

You use the Flex & Follow setting to enable Flex Time for a region

And it seems like Logic may be messing with the whole track even if you disable Flex and Follow on some regions, getting us back to the potential audio corruption we're trying to avoid. 

I really don't know. But a true "keep-your-hands-off-my-No-Flex-regions" would be handy 🙂

 

 

 

[Dave K]

 

Folks, there’s a wealth of experience and valuable input here, and I’m extremely grateful to you guys. Let me try to summarize the takeaways for any other novices that may stumble on this thread and to make sure I got this straight.

1. Flex is cool and fast, but also known to be buggy and distort audio on occasion.

2. The best way to sandbox Flex is to:

   a) let it operate only on select problem regions, not the entire track;

   b) do those regional Flex operations on separate throwaway tracks. Since Flex Pitch tends to be buggier than Flex Time, use separate throwaway tracks: one for Flex Time (only) region edits, and another for regions requiring Flex Pitch or both Pitch and Time; and then

   c) bounce or copy those regions back to your main, un-Flexed track as soon as they sound right.

3. In order to keep your original audio pristine, keep it in a Track Alternative that doesn’t get touched, and keep your candidate/working/“comp” track, the ultimate destination for all your edits, in another TA.

4. Optionally, keep any number of additional TAs with descriptive names and containing specific regions, to keep track of intermediate Flex or other edits, before copying them to the final “comp” TA, so you have a history of where they came from and a place to fall back to if needed, without needing to start over with the raw original.

Did I get this right?

Now, to go back and start over with my piano track edits and see how things turn out… 😅

 

[polanoid]

5 hours ago, sunbrother said:

Technically, yes, but that forces the track's Flex mode into Automatic.

It sure doesn't here, just double checked this

2 hours ago, Dave K said:

Flex is cool and fast, but also known to be buggy and distort audio on occasion.

That distortion is caused because Flex Pitch isn't designed to handle the polyphonic audio material you applied it to. Thats not "buggy".