E6 is a major sixth chord made of 4 notes: E, G♯, B, C♯. It sounds sweet and old-fashioned, and you hear it in swing, country, surf and the last chord of a jazz tune. It is the I chord of E major and turns up in 5 other keys.
The library above opens on E6 with 14 shapes up and down the neck, starting with hand-checked ones. Tap a shape to hear it, or play it one string at a time.