Music is a critical part of a praise service, but it is not always appropriate for other services, such as vigils.
The role of music in the bible is widespread, and there's no right or wrong way to use it. Whether you listen to the music, sing along, or ignore it.
A very common use of music is to take the worshipper on a journey. At the beginning of the worship, some uplifting songs to get people in the spirit, and then using slower, quieter songs to take them down into self reflection and confession. Then, positive, upbeat music to end on a high. It's not uncommon in churches with a younger demographic for these later songs to be rock songs, or very contemporary songs.
There are certainly inappropriate uses of music. Music that detracts from the purpose of the service is inappropriate, which is why you won't usually find music at a vigil service, and the songs at a funeral aren't usually rock songs (although sometimes that could be appropriate, depending on the wishes of the family)
As for the roles, this depends greatly on the exact congregation you're in. At some, the worship leader (pastor, priest, etc) needs to maintain control over music and song selection to ensure that appropriate songs with appropriate lyrics are chosen. Others this is entrusted to a lay person with good biblical knowledge, but often there are both people and they work togther.
For the congregation, I'm of the belief that they should take whatever role they are most comfortable with. Some (most) will sing along, others will listen, others may feel the need to dance, raise their hands, and others (particularly teenagers during a traditional service with hymns from the 1700s) will just ignore it and wish they were elsewhere.