M1, at least the OS X version, has no "stop" button, so maybe it'd be best just to remove the stop button and have only the pause button there instead. It'd certainly avoid tech support issues like mine in the future.
All versions of M1 have issues with stuck or bad notes, mostly if switching between two ROMs using one of the more CPU intensive hardware sets being emulated (F3 for example, which is notorious for not liking a song being played when opening those ROMs).
The issue of being paused using the Pause button and not being able to open a new ROM and listen to it is a weird one though. I typically will pause a song so I can get in my head a few of the notes of the song I might want to listen to, which in turn helps me remember its name.
One thing I would like to put in as a request, if you can get it in a future version: Please make the ROMs list a bit bigger onscreen. The text (and thus finger "clicking" width) is really, really tiny, making the single line entries a royal PITA to select.
Oh, and while I remember (since I forget really easy these days), whenever I leave a ROM playing and want to switch to a new ROM, I have to select (click) it twice in the list before M1 switches to it. I could click it once and wait forever and nothing will happen, but the moment I click it a second time it finally switches.
I wish I could code worth a damn - then I'd be useful for something other than a bug report or the like. I can easily design a workable UI via storyboard pics, but coding it...beyond my abilities right now. I used to go "fix it fix it FIX IT ALREADY", and then I wised up and finally saw some articles on just what emulation entails and I was like "wow, if I'd known this stuff before I'd have been more along the lines of asking what to do to work within the limits and less being an asshat just barking at the authors".
As for Richter's mention for DroidSound....that app is making me go completely NUTS. It absolutely, positively, cannot
handle large ROM sets. I have all of the SNES ROMs publicly released (both english and japanese), from A to Z and even segmented into half the alphabet for each respective region, DroidSound chokes and crashes (auto-quits) less than four seconds into the indexing process. I can't select the default indexing option as it doesn't find the ROMs (mostly because they were named before proper >31 character+extension filename systems were implemented, thus lack a visible .smc or .spc in their names. I have to choose Full for the indexing and it makes DS choke.
Hopefully I can find a workaround for that one.