C/B♭ Piano Chord
C/B♭ is a C Major chord played over a B♭ bass note. B♭ is not one of the notes of C Major (C – E – G), so C/B♭ is an added-bass (true) slash chord — the bass adds a new colour underneath the chord without changing the notes on top.
The dark key is the bass note (B♭); the coloured keys are the C Major chord tones.
Notes in C/B♭
Low to high: B♭ (bass) , then C – E – G.
How to play C/B♭
Play the bass note B♭ low in your left hand, and the C Major chord (C – E – G) in your right. Keeping the chord shape familiar in the right hand and just changing the bass is what makes slash chords easy to read and play.