Hello @BuG thanks for getting in touch with us.
I have looked into this issue that was previously reported to us and confirm that the Match Intro music that you hear, the Countdown, the End of Round and the End of Match music cues are not something that a player can disable using the Music Volume setting in-game. This will only disable the menu music, this is by design which our Siege team have confirmed for me.
I am sorry if these musical cues cause you distraction or discomfort in-game, I will happily pass your feedback on about it to the team however.