Two tunes (music) at a time

When I was doing some experiments with command block, I realized that two tunes are happening at the same time. One is (I guess) calm tune and the other is piano tune. During this, I also switched many time between the pause menu and real time playing. When I switched to the pause menu, the music or tunes stopped. But when remaining on pause menu for more than 10 to 20 seconds, the tunes do not start from where it got paused! This may have cause the problem running two tunes at the same time. No possible screenshots 😛