I believe that when you are playing your Tyros in accompaniment mode, the left hand is channel 2. You will want to change the settings on your Harmony M to receive messages on channel 2 instead of the default which is channel 1.

Or you could go to Function/Midi on your Tyros and create a midi setting so that left hand chords is channel 1 and right hand chords is channel 2.

I'd have to look at the manual to get more info.

Beakybird