adimatis,

Really don't need a mixer. The TC Harmony M connects to the Mic/Line in of the keyboard. The MIDI files are fired from the laptop to the keyboard's host/midi connection. MP3s are fired from the laptop's headphone out directly to one of the the amp's auxiliary inputs. The keyboard's standard audio output is fired directly into the amp's main inputs. The phantom power required for a mic comes directly from the TC Harmony-M.

You can use a mixer and do the same thing, but that's one more piece of equipment to lug around and a lot more wires to plug in. The end result is the same.

Gary