This article is partially a comment and followup to the article posted here: Two Ways To Sum
, and also another Tip and Technique, so I made it a new article. Please read "Two Ways To Sum
" first. Pro Tools is used as an example here. If you don't use Pro Tools but still question the sound of ITB summing in the DAW you use, the tips should apply equally.
Be aware that although bouncing is avoided by this method, you'll still end up with a pair of audio files that need to be stereo interleaved - another summing step is required. Otherwise, you won't get a single stereo file that is playable on consumer systems. For instance, if you import your two files into iTunes, they'll import as one file each rather than a stereo mix.
There are programs that can perform a stereo interleave outside of Pro Tools if you still want to avoid bouncing to disk, but these too will perform a sum to make the tracks a single stereo file. It becomes a tradeoff between preferences. Do you still like the sound of your mix after summing the L/R files in another program? Or if you compare that sum to bouncing the L/R files down to stereo interleaved in Pro Tools, does it sound the same, worse, or better?
If the files are going to be sent to a mastering engineer, then you should have no summing issues to think about. A real mastering engineer will probably have better summing tools than what you have at your disposal, and any audio degradation caused by summing should not be noticeable. If the ME's mastering rig is the same as your DAW, I'd say go one step higher and get another ME.
Checking to see if your files null is important. You can do this in a session containing a version of the bounced to disk mix, and another version of the same mix created by using the method outlined in "Two Ways To Sum
." Line them up so their start times exactly match (easiest way is dragging them to 0:00.000). Insert a plug-in that has phase reverse capability on the bounced mix (or the other mix, either one) and hit the phase reverse button(s). Hit playback. The files should null, meaning you hear nothing. If they don't, something is wrong with either bouncing to disk, or recording the mix to a stereo track. You don't have to figure out what's wrong, you just have to decide which sounds better to you.
Many engineers will argue that if the files null, there can be no difference between them, because the difference is neither audible nor measurable. However, if you're sure you hear a difference when listening to the individual mixes, it comes down to using your ears and deciding which method sounds best to you.