I have the same behaviour but only when playing a single girl in 'full size' mode. The music starts but doesn't stop, just plays and changes songs continuously regardless of whether there is a girl's clip being played or not, including ignoring when the next girl's show starts.
However, when playing a single girl in 'small size' mode the music works as expected, starting and stopping with the clip. If I 'enlarge' the girl during her show, the music just runs continuously and will not stop until the next show appears and I 'reduce' the size of the girl, when the music will end when her clip finishes.
Would be good if the same music behaviour occurred for both the 'full size' and 'small size' modes.