"There ain't absolutely no problem to connect your headphone output with 2 mono ( or 1 stereo ) inputs of your mixer.
Also the main keyboard ( L + R ) can be used simultaneously.
4 outputs to your mixer."
There ain't?
Just funning with you.
So I imagine the headphone output is a summing ( not that I technically know what summing means!) of both sides of the stereo field?
Related: Have you tried the Yamaha music soft MIDI tracks? Some of them are really excellent. I cannot swear by all of them... but I got mostly lucky in choosing about 55 of the 70 I purchased ... they are so well done. They have completely changed how I approach a gig. They sound too good, not to use them.. and so far, I just play over them while people dance!
I bring this up because it is vital to have the whole stereo field of these MIDI tracks to be heard... The headphone output seemed to be ok... but frankly, I was aurally surrounded by the stereo monitors... so I am not positive the headphone output was ideal. The pressure of an outdoor job did not afford me a chance to judge the result of using a headphone output.
My understanding of the outputs on t4
if I put drums eg, in the 2 main outputs, the drum will NOT be available in any of the other outputs.