How do you play the C undefined/A chord?

To play the C undefined/A chord on piano, play the C 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 C undefined/A chord?

The C undefined/A chord uses the 0 notes of the C 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 C undefined/A chord means a C undefined chord with A in the bass.

C /A

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

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

How to play the C undefined/A chord

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