BmMaj9 is B, D, F#, A# and C#. It keeps every note of and adds the .
BmMaj9 and both contain the 9th. The difference is the 7th: BmMaj9 uses , while uses the flat 7th.
Choose between them by the seventh under a held 9th. The minor 3rd remains in both chords.
Also written BmM9, Bm(maj9) or B-Δ9.

The bassist has the root, and the guide tones imply it anyway. The freed finger adds a tension. Playing solo, keep the root and drop something else.
How you get to it. The turn that lands on BmMaj9 is to : the ii and the V of B minor, which is where a minor tonic is usually arrived at rather than simply begun on.
Hear it land:→→
Contains BmMaj9 and adds eleventh and flat thirteenth.
Contains BmMaj9 and adds eleventh and thirteenth.
The common shapes and the derived voicings come from different places, and both are explained in how this site is built.
Shows each chord the way this style would voice it, and marks which of its alternatives belong to the idiom.