Three musicians are playing in a band.
The rock band is playing to a sold out crowd
We have no idea what type of band it is, it could be a rock band or may other possibilities. We also have no idea they are playing for a sold out crowd. They could be in someone's garage or anywhere.
Just because a band is playing does not mean it is a rock band or they have a sold out crowd.
It doesn't say the genre of the band is rock. It also doesn't mention ticket sales or the amount of spectators, so we can't assume they are playing to a sold out crowd.