In Task Manager and Resource Monitor, I'd start looking at stuff like this when the music slows or stops:
Processes running for all users: how many? Which are occupying the CPU?
RAM: details on what is shown in memory tab of Resource Monitor when slow? how much used, available, cached, reserved, etc.
I'd also take a look at what is running on startup by default by using msconfig.
And I'd do a full malware and virus scan.
Have you knowingly made any configuration changes or added any software/hardware?
If it's a new development that was not there yesterday, something must have changed. Unless it's imagination.