Silencing the melody: not the Chord changes

Hello,
I put together a tune in standard Jazz lead sheet form. For playback and exporting purposes, I'd like to have the option of muting the full melody of my tune, but not the chord changes. I've tried going to the 'mixer' in an attempt to do so, however, the mixer presents one channel- 'piano' which is baically the chord changes and melody together in one channel.

I've only seen thus far instructions for muting chord changes [...specifying not written out chords] in playback or a couple of notes, but how can it be done if both are on one channel? Is there some option allowing me to somehow have playback of the chord changes/progressions without playback of the melody?

Thank you for all responses.