Ideally, two sounds with a phase difference of 0° should have double the volume, and a phase difference of 180° should cancel the volume. However, Scratch has a hard time starting and keeping layered sounds in a consistent phase, especially if lag is present. As far as I know, this is unavoidable, even (to a lesser extent) on Turbowarp. This limits the sound emulation quality on Scratch when using FFT and similar algorithms by creating a buzzing/reverb/muffled effect. As a result, it appears many other Scratchers, including @Kouzeru and @52525rr , have decided to omit phase entirely and instead play unshifted sine waves with a volume proportionate to each complex factor's magnitude. Going forward, I plan to do the same thing to save memory.
