Reply To: suggestions needed on the best way to do simultaneously tap tempo with my H9 and TF via FS3X

[nickrose]

You would want to use a TRS (stereo) Y adaptor. The switch would then control both units.

But, you would be creating a ground loop, so might have to fiddle with the wiring to avoid hum.

A switch will work better for tap than MIDI, which is inclined to be a little "rubbery."