What does the music symbol notification mean

I’m using my son’s hand-me-down Samsung S5. It runs Android 6.0.1

A few days ago, a music symbol (quaver) appeared on the notification bar. When I pulled it down, there was just the music symbol with no text next to it. When I tapped on it, nothing happened and the symbol disappeared. The next day it appeared again. I did the same thing and it disappeared again. This morning it appeared again.

I’ve done an internet search for notification symbols but I cannot find this music symbol or what it means.

What does this music symbol mean?