Identify components in an audio circuit schematic
I'm trying to determine what kind of component is R-CH and what role
it plays in the circuit.

R-CH is the right-hand channel. Above it you see the circuit for the left-hand channel. The total circuit is for a stereo amplifier of some sort that has left and right channels.
They don't bother showing the right-hand circuit details because it's a repeat of the left-hand circuit.