Pentatonic

Five notes, zero wrong answers

The pentatonic scale removes the two notes most likely to clash, leaving a shape that sounds good over almost anything.

The formula

major    1 2 3 5 6
minor    1 ♭3 4 5 ♭7
sound    safe, bluesy, instantly melodic

Why it matters

It's the first scale every guitarist learns, and the one most solos are actually built from. If you only learn one, make it this.