TL:DR: re-add the toggle music notes button to headphones, so they don't have to be used as only an instrument, positive & beneficial change for immersion reasons without negatively affecting anyone.
So, headphones used to just be an accessory, where you hit a button and it toggled the visible music notes around your character. At some point it got changed to an instrument, where you copy and paste the music pattern, like any other instrument.
Now, I can maybe understand the reason for this, but I am going to go out on a limb and say I never see anyone really using the headphones aside from myself, and that going back to the original would probably not affect too many people. I would not be surprised if it was arbitrarily added because TG code had this functionality just to match with them. I initially was going to ask to revert the headphones back to their old function of just a toggle button, and then Charlie pointed out that the option to toggle could just be added in addition to the instrument function.
I know this seems a minor change that will have no big impact, but I think it would be helpful for cultivating a more real and immersive experience for some people without inhibiting anyone else. I usually used the music notes when listening to music irl, and had it more or less as if my character was listening to that music. It also opened up conversations where people asked what my character was listening to IC, and led to some nice IC chats about music. I would not be surprised if more people used it for this reason if it were to be re-added.