OK, that got a bit strange. This Project has (actually it did have but I didn’t know it at the time) 32-bit files, so I thought this should work. I rendered a Track to 24-bit and it quantized just fine. But then I went to the Pool to set the new file to Musical Mode and noticed that I’d already converted all the other audio to 24-bit when I first resurrected the Project. So none of the files are 32-bit.
Still none of these ‘original’ 24-bit Tracks will quantize. So I suspected the 32-bit-ness didn’t matter since I had 24-bit files that wouldn’t quantize but if that same file was rendered into another 24-bit file it will quantize.
So I built a little test case with a VSTi, 2 bars of four 8th notes each slightly off of the beat. Then I rendered this as both 24 and 32 bit. Both of those quantized fine. I also checked to see if having Musical Mode on or off mattered. It didn’t. I played around with this test rig a bit and could never get audio files that would not quantize. So…?
Probably time to fire up Melodyne.