I have a Casio CT-655 (it's old, I know) and it has a system where each channel can be a different instrument. The first channel works fine, but when i try to use any other channel, it typically holds the note after i release the key, and doesn't stop until I click the drop down menu that shows the different MIDI instruments connected. it also plays the instrument on the first channel about 10-20% of the time. I don't know if this is just a glitch or if there is a way to fix it. if is a glitch, it needs to get patched. And also, like i said, the keyboard is old, but i haven't had any trouble using those buttons for other functions that the keyboard has when it is out of MIDI mode.