music playing randomly on mac

It might be easier for you to get help with your question with your Mac if you were to change your subject line. If there’s a subject line that just says something vague like weird issue then we don’t really know what is that you might need help with until we open the post. I don’t have a Mac myself so unfortunately, I’m unable to help you with your question but just thought that may be helpful if you had a more specific subject line so people can help you better.

What was the question?

For starters, it's probably best to upgrade to Tahoe, and secondly if you're using multi-point headphones, your iPhone might be automatically connecting to them to play audio. AirPods and Beats headphones are less likely to display this behavior since their integration with the rest of the Apple ecosystem means that Apple devices will only attempt to connect when Apple thinks that it makes sense (I usually have this disabled on the AirPods that I use at the computer and enabled on the AirPods that I use away from home). Also, the Music application on all Apple devices automatically stops playing whenever the audio device that it's playing through is disconnected, to prevent situations like those that I used to experience at work back in the day, when I disconnected my headphones from my work laptop and the music that I was listening to started blasting at full volume out of the built-in speakers, or even worse, when the audio driver suddenly thought that I had unplugged my headphones and all my coworkers were treated to my metal and electronic music taste until someone bothered to come over and tap on my shoulder (I even had situations in which people just started dancing at the rhythm of my music as a joke to get my attention).

My theory is that when your iPhone plays audio, your multi-point Bluetooth headphones automatically switch to it, and the Music application on your Mac stops playing as a reaction to the headphones disconnecting.

Just had this tested with a Twelve South AirFly Pro Deluxe, which is a Bluetooth dongle that connects to analog headphone jacks and can advertise itself as either a speaker, taking Bluetooth audio as input and delivering it as analog audio, or as a Bluetooth player, receiving analog audio as input and delivering as Bluetooth audio, and is also a multi-point device that I keep paired with my AirPods 4 and AirPods Pro3 at the same time since my primary use for it is interacting with the screen-reader on ATMs here in Portugal. In this test I just turned the AirFly on and it immediately pulled the AirPods 4 that I'm wearing right now from my Mac, where my music was playing but stopped automatically, and when I turned it off my AirPods reconnected back to my Mac, however the Music application did not pop in front of everything else.