Hi Trev

Just done some test
And can confirm that the midi slider in the mixer melody track works fine for me.

With a three realtrack style and a midi melody track.

It works sending the midi to the coyote internal dxi or to a midi driver then out to an external midi synth module or my clavinova

I made the melody midi track by first importing a midi super track I then changed the patch to gen midi, and then told it no real track this left the notes on the melody track to play any midi voice and the melody track displayed in yellow
Track volume slider fully effective.
So your problem is a mystery.
Mike

BIAB2021 UltraPlus,AsusN55S1Tbssd, W10/64,Akai EIEpro
Yamaha CVP405,SquireStrat, CoolsoftVMidSynth
Novatation Impulse61 Ctr kbd, Cwalk blab Kontakt

http://mikesmusic.byethost16.com/