Here is a throwback game that now can be played easily in this Internet age. Assemble a list of popular songs from iTunes. (Some of the teens can do this for you!) Set up speakers so you can play portions of the songs to a larger group.
Create two teams (as you would with charades), and then invite one person from each team to take the challenge to name the tune you will play. However, instead of notes, they have to say, “I can name that tune in three seconds (two seconds, one second, etc.). Whoever accepts the challenge must then name the tune, hearing only that short snippet of music. If they lose the challenge, the other team gets the point.
If you create a file of 25 to 30 songs, you should have plenty to play a 15-minute game.