Varispeed again

There are a couple of threads now talking about the subject but maybe it's me but things are not so clear ATM and Logic Manual doesn't help much... sorry if this is a kind of double post, but after reading both threads and after experimenting with Logic I still have doubts and I'd love if we find a proper way to work sharing our experiences. Here are mine and some doubts too. Please comment and feel free to correct me as much as needed

to change speed we must FIRST turn Flex on, select an apropiate algorithm for each track and then change tempo value. (In my experience changing tempo first and then activate flex leads to bad results)

once I find a new tempo that pleases me I have a few choices and questions:

1: just keep working as it is. This leads to doubt about what happens to the old audio sound quality but most important: what happens to new audio recordings. Are they OK or will they suffer some degradation because the speed being in "variable" mode?.

or 2: "fix" the project to the new tempo. This is my preferred way: bouncing in place the varispeed files and turn varispeed off at the new tempo.

the files can also be changed using Time Machine or other programs, I don't have experience if this is advisable or not to maintain sound quality.

Another thing which is related and I don't quite understand is the way the new Advanced Tempo Detection works. I understand how to use it with constant tempos (Live style...), but I'm mostly interested in recording with Free Tempo and have the program follow it (not changing it). I suppose it'll work OK with drums or rhytmic sources, but with piano or guitar and voice works not so well here. There's any explanation (at least I did not found any) about how to modify the tempo markers, and guessing is not working very well for me. I managed to "fix it" but it implies FLEX, mannually changing Tempo list and cut and move parts of the recording; and even if that did what I needed it was tedious and I ending altering the flow. I'd love to read some experiences about this.

to change speed we must FIRST turn Flex on, select an apropiate algorithm for each track and then change tempo value. (In my experience changing tempo first and then activate flex leads to bad results)

Right except for selecting an appropriate algorithm for each track: Logic chooses the appropriate algorithm for each track, so that you shouldn't have to do it. Check the chosen also and change it if you'd like, but in a normal workflow there's no need for that step.

once I find a new tempo that pleases me I have a few choices and questions:

1: just keep working as it is. This leads to doubt about what happens to the old audio sound quality but most important: what happens to new audio recordings. Are they OK or will they suffer some degradation because the speed being in "variable" mode?

I'm not sure what you mean here. There are no old and new audio recordings. Flex is non-destructive, meaning it doesn't touch the audio recording that is on your hard drive. It loads that audio file in RAM and modifies the way the file will be played back from RAM. The file is unchanged. The only sound degradation you get is what you can hear when you press play, so use your ears to determine whether or not the result works for your goal.

or 2: "fix" the project to the new tempo. This is my preferred way: bouncing in place the varispeed files and turn varispeed off at the new tempo.

the files can also be changed using Time Machine or other programs, I don't have experience if this is advisable or not to maintain sound quality.

Generally I get better results using Flex than Varispeed, but experiment and find what works best for you and the material you're currently working with.

Another thing which is related and I don't quite understand is the way the new Advanced Tempo Detection works.

That's not really the same topic so feel free to start a new thread for that specific topic.

Thanks you for the answer!

I was under the impression that recording audio while in Varispeed mode could present clock problems, but your explanation suggest it doesn't, so great. I prefer to take the Bounce In Place route for the tracks that were speed altered mainly for peace of mind reasons as 99% of the times I record them again later, and for disabling varispeed mode. Both ideas seems irrelevant according your explanation, and it's great news as it saves me both steps.