[in menu Modify/Volume operations]
This operation removes the notes from melody channel. That is useful for karaoke purpose or to play the melody self on a MIDI keyboard along to the remaining song accompaniment.
First you need to define the MIDI melody channel of the song once in the MIDI descriptions of the file. This operation automatically starts the description dialog if the melody channel is not set.
The description dialog offers also to define a transpose value for the MIDI file. This is useful when your score sheet contains the notes in other song key and the notes (except drums) will be automatically transposed to same song key when applying this operation.