Bmaj9 is a major ninth chord made of 5 notes: B, D♯, F♯, A♯, C♯. It sounds rich and floating, and you hear it in jazz, R&B and cinematic pop. It is the I chord of B major and turns up in 3 other keys.
The library above opens on Bmaj9 with 14 shapes up and down the neck. Tap a shape to hear it, or play it one string at a time.