The parent comment was comparing DJ equipment to a record player (to this patent), which I feel is a poor example because modern DJ equipment almost always has different equipment too rather even if you could technically do it with a fader and some record players (as in at a gig, I'm aware people still mix on vinyl - pretentious as it can be).
The patented guitar thing is literally played the same way but in a different place, which I think should really be considered prior art unless the fashion aspect is considered rather than purely functionality.
I think part of the reason people are chiming in on the distinction is that a controller is comparable to a mouse for a computer; a controller requires something else for any functionality, at which point you're comparing a general computing device that can do anything to a much more restricted special use device
