Under the Controls menu there are three options that are available when playing a song:
- Suppress Left Channel Vocal
- Suppress Right Channel Vocal
- Suppress Center Channel Vocal
You can also show the "Lead Vocal Channel" Sort Column, to see which songs have a setting applied. Learn how to hide and show Sort Columns.
Multiplex: Left and Right
Vocal Reduction works perfectly with "Multiplex" discs and songs.
When you suppress the Left or Right channel, kJams simply takes the opposite channel and duplicates it into the target channel, effectively eliminating the target channel. This is useful when there are vocals only in the target channel, such as CD+GM discs (multiplex), and will perfectly eliminate the vocals. kJams will remember your setting, so the next time you play the same song, the setting is applied.
When you suppress the Center channel, kJams simply subtracts one channel from the other. Presuming the Vocal was mixed directly in the center, this will do a fair job at removing the vocal, however this is not always the case. You'll have to try it on a case by case basis, some songs will sound terrible using Center Channel Suppression.
For a detailed explanation of Center Channel Suppression, see this article.
In the future, I will allow Audio Unit plugins, at which time I will recommend Vox Reducer. Until then, if you really need better controls, you can use GarageBand with "Vox Reducer" to generate your audio track, then bring that back into kJams.