piano chord
B6
B1D♯3F♯5G♯6
A major triad with a sixth added. The same four notes as a minor seventh chord a third below.
What is true of it
B6 is B, D♯, F♯ and G♯ — 1, 3, 5 and 6 counted from B.
These are also the notes of G♯m7/B and A♭m7/B. Which name is right depends on what is underneath and what came before — the notes alone do not decide.
On an instrument that cannot reach all 4, the 5 goes first, in that order.