Recently I went back to the same studio and changed a few lines of the vocal, as writers are known to do. When I pull up the old track and the new track together on my PC as .wav files I noticed the new sine wave was flipped upside-down from the old one. I merged the files, cutting pieces from the new one and inserting them into the original file. F irst we need to get squared away on our terminology. Unless the engineer recorded actual sine wave tones on to the ADAT your waveforms were not sine waves.
Sine waves correspond to a pure tone.
Since we don't know what was really recorded we'll leave that at that. Normally complex music waveforms are so complex that polarity or phase is not easily observed. However, if one zooms in far enough it is sometimes possible to see these types of inconsistencies. We do not doubt what you say you saw, we're just providing a little background so other readers can get on the same page with us. W ith the above caveats in mind, your assumption is basically correct.