Amplification

A booming soundwave blasts from your instrument in a line 100 feet long and 5 feet wide in a direction you choose. Each creature in the line must make a Dexterity saving throw. A creature takes 8d6 thunder damage on a failed save, or half as much damage on a successful one.

At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, the damage increases by 1d6 for each slot level above 3rd.