How do you play the B undefined/A chord?

To play the B undefined/A chord on piano, play the B undefined chord ( and undefined) with A as the lowest bass note. Place the A note below the other chord tones. Slash chords specify a particular bass note different from the chord root.

What notes are in the B undefined/A chord?

The B undefined/A chord uses the 0 notes of the B undefined chord — and undefined — with A played as the bass note in the lowest register.

What is a slash chord?

A slash chord (or compound chord) is written as Chord/Bass and specifies both a chord and a bass note. The note to the right of the slash is played as the lowest note. The B undefined/A chord means a B undefined chord with A in the bass.

B /A

The B undefined chord consists of the notes, with A as the bass note.

Piano keyboard showing the notes for a B undefined/A chord

How to play the B undefined/A chord

Play A as the lowest bass note in the left hand
Find B (Root) on the piano keyboard
Press the note to sound the B undefined/A chord