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Ways to change speed of an audio file or project


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Hi All,


I am looking for different ways to change the speed of an audio file, or a project full of midi tracks.

Sort of going for the effect of varispeed, but it would be nice to *automate* the speed change. I am currently automating tempo in the global settings, but I'd like to go one step further.


The effect can alter the pitch, or not. If there is a way to choose, I'd like to hear both ways! Really just looking for all of the possibilities here that can be automated. Do I need to buy a particular plugin?

Thanks in advance!

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MIDI will follow the changes you make in the tempo track. Audio will too, if you first Flex enable all the audio tracks and use the appropriate Flex mode for each track. (BTW, you can change Flex modes after the fact; that will not alter the detection process.) And make sure you check the "complex" box if you choose Polyphonic mode for tracks like guitar or piano. This makes a big difference in the quality of the sound of the flex rendered file.


Generally, the cleanest way of changing tempos is to make one global change to the tempo, (one new speed for the whole project) by changing the tempo either from the Transport or from Global tracks / Tempo / Tempo alternatives.


Making tempo changes to specific areas via a tempo track requires a little more finesse when audio files are part of the project. For instance, if you are including tempo ramps where the tempo changes gradually, then you are likely to get glitchy results from the previously recorded audio in the area where the tempo is ramping. I get around that by increasing tempo in short discrete sections. Of course, if all you have is MIDI in the project, then ramp away to your heart's content.


The other thing is that even an abrupt tempo change (IE instantly going from 110 to 114 bpm), if done in the middle of a held note in the audio recording, will also create a small glitch. So the solution here is to automate the tempo change when there is a pause in the audio (no sound) or insert the tempo change right on a transient or vocal consonant. It really depends on a number of things and how many tracks you have. You might find that only one audio track has a glitchy sound because of the tempo change if you solo it but you may not be able to hear that in the context of a full mix.


Using Varispeed is a whole other topic. IME, I don't find Varispeed to sound anywhere near as clean on audio files as when I change tempo with Flex enabled tracks by the methods described above. However, if you want to change both the speed and the pitch at the same time, Vairspeed is very clean. I don't think you can automate varispeed to change in the middle of a track, however.


And here is yet one more method of changing tempo on a specific area, again using Flex....


Say you have recorded a live performance of a band (off grid, no click) and you want to copy a really great chorus over to another part of the song. But when you do this, you discover that the chorus is too slow when you paste it in to that other section. If you Flex all the tracks first then you can select just the copied regions and Option-drag the right side of them to make them slightly shorter and therefore slightly faster. I've done this a few times and it works very well as a way of matching tempos between sections.



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