A well designed ported sub can be just as good for music as a sealed sub. There is a difference in behavior around the port tune however - given two subs with the same driver a ported design will typically have more output down to the port tune, but will then rapidly fall off. The sealed sub will start to fall off sooner but will have a more gradual roll off.
Typically a ported sub will have a larger enclosure than a sealed sub, however, so sealing a ported sub may hamstring its performance potential.
Typically a ported sub will have a larger enclosure than a sealed sub, however, so sealing a ported sub may hamstring its performance potential.