Stacking tracks of the same instrument can create phase problems so your concern is valid.
But if you record the tracks differently (different mic / preamp, placement...) you will reduce the risk of noticeable phase problems.
Altought it may not give a good stereo image for a chamber session, if the second take is pan differently it will also help.
Even changing the musicians position in the room and exchange where they site in relation to each other can help.

Since there can be no phase coherency between takes, the only way you can get phase problems when live recording is by poor microphone positioning on a take and not by stacking multiple takes,. This means that you should consider how you choose and position your mics to capture your 8 players, but you only need to consider it in the context of it being a single take.

However, over-dubbing string parts does raise two other points:

The first concerns monitoring: are you going to provide each player with IEMs, or will there be a conductor wearing headphones, hoping to keep the string players accurately in time?

The second point is that you can create a much better spatial effect in the result by moving the players around between takes, but keeping them within their section. If you are going to do this, you have to think even harder about initial microphone choice and positioning, as you should not move the mics between takes. So, for example, the two cellists could be front desk players for take 1, moving to second desk for take 2 etc. The fiddlers could swap their positions around between takes to distribute the individual tonalities. When I first tried this technique, I couldn't believe how much better the overall result was in space and depth. I got the size of a small orchestra out of only a handful of players, but I was lucky that I had the choice of seasoned session musicians to work with.

pcrecord, post: 448893, member: 46460 wrote: Stacking tracks of the same instrument can create phase problems so your concern is valid.
But if you record the tracks differently (different mic / preamp, placement...) you will reduce the risk of noticeable phase problems.
Altought it may not give a good stereo image for a chamber session, if the second take is pan differently it will also help.
Even changing the musicians position in the room and exchange where they site in relation to each other can help.

Thanks for the response, we are considering a second set of microphones, but I am also intrigued by the spatialization advantages of asking players to move slightly, as Boswell mentions later in the thread.

Boswell, post: 448896, member: 29034 wrote: Since there can be no phase coherency between takes, the only way you can get phase problems when live recording is by poor microphone positioning on a take and not by stacking multiple takes,. This means that you should consider how you choose and position your mics to capture your 8 players, but you only need to consider it in the context of it being a single take.

However, over-dubbing string parts does raise two other points:

The first concerns monitoring: are you going to provide each player with IEMs, or will there be a conductor wearing headphones, hoping to keep the string players accurately in time?

The second point is that you can create a much better spatial effect in the result by moving the players around between takes, but keeping them within their section. If you are going to do this, you have to think even harder about initial microphone choice and positioning, as you should not move the mics between takes. So, for example, the two cellists could be front desk players for take 1, moving to second desk for take 2 etc. The fiddlers could swap their positions around between takes to distribute the individual tonalities. When I first tried this technique, I couldn't believe how much better the overall result was in space and depth. I got the size of a small orchestra out of only a handful of players, but I was lucky that I had the choice of seasoned session musicians to work with.

Thanks for the advice. I like the idea of creating the spatialization by moving the players. It makes a lot of sense that the players would thus create more space and depth in this method. And it does also get closer to the natural positioning of the strings in relation to one another in an orchestra or large section.

All you need to do is move the microphones slightly so the new tracks sounds slightly different, spacially. I wouldn't worry about any phasing issues because this is exactly why strings sound so good - the timing of the playing and the pitch create the lovely chorusy, thick sound. If you can sort the monitoring to enable them to actually play, just do it. To be honest, I don't think I've ever even moved the mics on many sessions. Are you miking individually, adding ambience artificially, or using a stereo technique?

paulears, post: 448904, member: 47782 wrote: All you need to do is move the microphones slightly so the new tracks sounds slightly different, spacially. I wouldn't worry about any phasing issues because this is exactly why strings sound so good - the timing of the playing and the pitch create the lovely chorusy, thick sound. If you can sort the monitoring to enable them to actually play, just do it. To be honest, I don't think I've ever even moved the mics on many sessions. Are you miking individually, adding ambience artificially, or using a stereo technique?

Thanks for the feedback. I am spot miking each string and using a stereo pair. I was considering either asking the string players to move slightly, or moving mikes as you suggest.
But I would have left stereo pair in place for all takes.

if you have both, then you probably already have some phase issues, that presumably are working for you rather than against. If you look at the process then if you move the players, you have to move the mics too, and leave the stereo pair fixed, but then you need to also shift the pan position of all the spot mics to match the stereo image, so I doubt that you can actually do this totally correct - in fact, if you left them in the original positions, you could just pan each take a little left or right - I've never been very good with spot mics in terms of making the spot mic position match the stereo image. At best, I can get it roughly in the right place left to right, but adding delay to shove it further away is really too subtle for me - so why not just record them - you have loads of mix possibilities - but phase is unlikely to be a problem with the second take. If it rears it's head it will be from fighting with the stereo field from the pair compared to the spot mic.

paulears, post: 448907, member: 47782 wrote: if you have both, then you probably already have some phase issues, that presumably are working for you rather than against. If you look at the process then if you move the players, you have to move the mics too, and leave the stereo pair fixed, but then you need to also shift the pan position of all the spot mics to match the stereo image, so I doubt that you can actually do this totally correct - in fact, if you left them in the original positions, you could just pan each take a little left or right - I've never been very good with spot mics in terms of making the spot mic position match the stereo image. At best, I can get it roughly in the right place left to right, but adding delay to shove it further away is really too subtle for me - so why not just record them - you have loads of mix possibilities - but phase is unlikely to be a problem with the second take. If it rears it's head it will be from fighting with the stereo field from the pair compared to the spot mic.

I am considering moving the players back slightly to achieve the spatialization that Boswell mentions higher in the thread. I keep them in relative pan position, but only further back from the microphone, and not move the spot microphones. agree that there is no totally correct way to do this.