E

E is the most natural key for guitar — the lowest and highest strings on a standard-tuned guitar are both E. E major and E minor are arguably the most-played keys on guitar. E major sounds big and bright, the open low E adding weight under every chord; E minor is brooding and resonant, the darkest-sounding easy key on the instrument, which is why so much rock and metal lives there.

The standard guitar tuning (E–A–D–G–B–E) makes E the fundamental resonant note of the instrument. Countless rock and blues songs are in E or E minor, from "Smoke on the Water" to Jimi Hendrix's "Purple Haze."