Amp

The Amp spell energizes and "electrifies" a stringed instrument.  The effect lasts 1 hour and amplifies the sound of the instrument so that it can be heard from 100-300 feet away (volume tunable by rotating a small disc that appears on the instrument with the numbers 1 through 10 on it.) 

Creatures and objects that are sensitive/vulnerable to loud noises are vulnerable to the music of the amplified instrument because it is now "loud" within half of its audible distance.  While the instrument is being actively played in combat, the Amp spell grants advantage to any concentration saving throws for bard spells and increases the range of ranged bard spells up to half of the active audible range.  (150 feet at level 1, 200 feet at level 2, etc.)  Non-Bard spells and spells whose initial range is "self" or "touch" are not affected.

At Higher Levels. When you cast this spell using a spell slot of 2nd level or higher, the audible range increases by 100 feet for every level above 1st.  (The numbers 11, 12, and so on appear on the disc for each higher level to let you crank the volume.)