I have a recording of a monophonic melody on violin, and another recording of the same melody on a saxophone. I'd like the two to sync perfectly, so I want to match the exact timing of the saxophone to the violin.
They're not recorded to a click track, but the saxophone player was playing over the violin recording so they are roughly in time. I just want them to be exactly in time.
Is it possible to automatically stretch and shrink the individual saxophone notes to match the violin?
Flex Time is your best bet for achieving something like this but it will not be automatic. Let me preface by saying I do use Logic but I’m not very experienced with the flex time features of the program. That means there may be a solution that I’m not aware of.
I think you have two options here. The first is to try an overlay a click manually over the violin part. Once you’ve done that you can use the quantize features in flex time to line everything up. The problem with this is if you apply quantizing to the violin part it will change the integrity of the original performance.
The other option which I think is the better one is to apply flex time to the saxophone part and manually move the notes to line up with the violin part. This will be visual and not use a click for reference. It will be somewhat time consuming but you’ll get it done. EDIT: As mentioned by @Edward you must also listen to your edits to make sure they sound the way they should.
If you had initially recorded to click this might have been an easier process but I think it can be achieved.
I have some personal rules relevant here..
My Personal Rule #1: Re-record if you can!
My Personal Rule #2: Do not stretch anything unless it's absolutely unavoidable. Stretching (here, meaning changing duration independent of frequency) compromises the integrity of the recording in some way, depending on how it's done. Most temporal aligning techniques use frequency-adjusting algorithms. Some don't, which is great, but they only tend to be useable in certain situations (like a clean drum loop). But they do that flawlessly. An example of this is the time-stretch option in FL Studio named, if I remember correctly, "slice map".
How I would do it...
I've never used Logic Pro, or flex time, but when I want to time-sync notes like this, in Cubase (this technique can be done in any DAW), I simply get them lined up at the start, then chop up the clip and line the notes up manually, while trying to respect the original intent of the player - you can use another track with the original recording as a performance reference. It's extremely easy if they're already "Roughly aligned", as you say. Some sequencers allow you to select the sliced recording and compress/expand the timeline just for those clips (i.e. increase/decrease the tempo for the sliced up audio) - this is extremely useful for this situation. The only tricky part will be sustained notes and complex articulations, but you can usually do it easily enough with cross-fading or even just fading in, the next clip. No automated process can do this as well as you can, if you have the will.
Note: This sort of editing does get easier with experience, and you come up with simple little bridging techniques, settings (like auto-fade on split) and even macros to simplify, enhance and make the process more efficient. But even with little editing experience, it should be easy enough for this. It will sound WAY better than digitally stretched and compressed notes.
