when the music plays and you set the music to off. the music will not stop playing it just plays really softly

can confirm
@@unknown You should not confirm your own reports. It's logical that you can confirm your own report. It just makes others think it's a fake.

To reproduce just use a command like

/playsound minecraft:music.creative music @a

and turn your master volume to 100% and your music to OFF (and if necessary also raise your windows sound).

This is also the case in 1.8.9