JP1 Remotes

When devices are too dissimilar to share a single protocol, keymoves are the best solution without a device combiner. Your bogus OBC on mute is also a good workaround.

Extenders and some remotes have keygroup mappings / activites where you can mix devices. Not sure which remote you are using these days.

The Mute glitch is on the One-For-All URC-3680.
My wife has a Charter OCAP C4000 URC-1060BC2.
The unassigned Mute was acting like a Power key [OBC = 0] on my Aiwa stereo.
Other tested unpopulated Mute assignments had OBCs of 0 & 255. Single devices retained their device numbers. Combo devices had unrelated device numbers.

Regarding your findings with the MUTE button, all JP1 remotes have 3 button groupings where it's "all or nothing", meaning you have to populate all of the buttons in the group, those groupings are:
* the 10 number buttons
* the 3 volume buttons (including mute)
* the 2 channel buttons

When you create an upgrade using RMIR, if you populate at least 1 button in a group, you have to populate all of them, and if you don't, RMIR will assign hex code 0 to the un-populated buttons. Typically, people don't notice because they don't expect the button to do anything as they didn't program it. But if you want to guarantee that it doesn't do anything, then you can program an OBC that you know does nothing, to it, like you did.

Good to know. Thanks.

According to Google's AI, the following describes Sony's Single Opera function:

Based on Sony boombox remote layouts, the "Single Opera" (or sometimes listed in manuals as "Single Operation" or similar CD mode functions) key is designed to control the playback mode of a CD.

Here is what it specifically does:

• Single-Track Repeat/Play: It is typically used to toggle through CD play modes, such as repeating a single track or playing only one track and then stopping.
• Disc Mode Toggle: On some models, it works in conjunction with "Disc Mode" to switch between playing a single track, the whole disc, or, if it is a multi-disc changer, a single disc.

Essentially, it is a shortcut to change the CD player from continuous play to single-track mode.