Hi Bill,....I absolutely love the TC Harmony Singer2 unit....
it really sounds good, vocal tracking is on par with all other TC units for singing. You can use it with any instrument besides guitar, digital piano, organ, etc, So easy to set up and use, excellent reverb and simple harmony selections at the touch of the dial and the Tone feature sets up the perfect EQ for YOUR voice also which you sing. I hook it up right into the EA7 Mic input and use stereo
L/R outs to my Pa system... I would imagine the TC vocal signal gets summed into the keyboard and the overall sound thru the keyboard L/R is stereo out both speakers. I am happy with it.