I have a music loop played as the background music of a battle scene. There are some control inputs in the game that would raise or lower the pitch of the music for a semitone for a short duration of time, resulting in minor change in tempo as well. The change of pitch is done by posting an event that would alter the voice pitch of the music audio bus.
However, after the pitch is altered, the tempo sync of the music is messed up. It seems like although the tempo of music is changed when pitch shifted, the background clock of Wwise still follows the original tempo, so the looping point is still based on the clock instead of where the music is actually played at. If I raise the pitch, the looping point will be dragged behind, leaving a short space at the post-exit; If I lower the pitch, the music loops back before reaching the post-exit part.
Another problem is, even when the pitch is altered, once the music loops, it always return to the original pitch, and the reset voice pitch action would try to "reset" the pitch again, resulting in an additional raising or lowering of the pitch. For example, if I have an event that raises the pitch for a semitone for 4 seconds and trigger the event 2 seconds before looping back, the pitch will be only raised for 2 seconds until it loops, and after it loops back to the beginning the pitch will be automatically reset. The reset event 2 seconds later would lower the pitch for another semitone, which will make the remaining music a semitone lower until it loops again.
Also, any other music such as stingers triggered during the altered pitch duration would have no effect and still plays in its original pitch. The pitch of music would only be altered while it already starts playing. So I guess the bug is, when a new music track gets played, it doesn't follow whatever voice pitch settings at its outputting bus.
I hope this issue can be solved so there will be more flexibility in the interactive music design by manipulating the pitch of music.