Some devices, particularly Apple devices, will upload huge amounts of data to its iCloud storage at times when you least expect. Android devices do the same too, but syncing with Google Drive. And Microsoft devices sync with OneDrive.
I had both cable and DSL internet in the past. On both types of networks, whenever an iPhone or iPad decides to backup or sync with iCloud, it uses up all of the upstream bandwidth. Since cable and DSL are asynchronous, that upload wipes out the downstream bandwidth. Doing a speed test on my PC at that time will show very, very low bandwidth. And ping replies shoots up to more than 1000ms instead of the normal 30-40ms.
I can say with high confidence that if your music is cutting out, it's probably due to an Apple device (or another mobile device) draining all of your bandwidth. Next time you see this happening, turn off every mobile device you have in the house. Run a speed test on your PC and see what your bandwidth is at that moment, compared to what it should be normally.