I use audio files to study; on left channel there is only the accompaniment, on right one accompaniment + melody.
If I play the audio with the pitch at 1,00 and I pan all to the left channel, everitying work fine and I listen the accompaniment without melody.
If I play the audio at a pitch lower or grater then 1,00 I still listen the melody even if I pan to left channel.
Under the audio player settings, is "Enable advanced audio player" enabled or disabled on your devices? I don't have good audio file to test what you are describing at the moment, so if you can send me one to test with at mike@zubersoft.com, I would appreciate it.
I have investigated this, and there is indeed an issue with pitch shifting and panning. For now, the only known workaround is to uncheck "Use advanced audio player" in the audio player settings which may not work on every device as the availability of pitch shifting with the default audio framework depends on the OS version of the device. I will have to spend some time redoing some of the audio processing to see if I can pan the audio first, then pitch shift and time stretch the panned audio to avoid this issue.