B♭m6 (also written A♯m6) is a minor sixth chord made of 4 notes: B♭, D♭, F, G. It sounds bittersweet, a little mysterious, and you hear it in gypsy jazz, film music and minor-key endings. It is the i chord of B♭ minor and turns up in 5 other keys.
The library above opens on B♭m6 with 14 shapes up and down the neck. Tap a shape to hear it, or play it one string at a time.