The third voice from the top lowered an octave. The dropped voice becomes the bass, which is why a string is skipped.
BmMaj9 is B, D, F#, A# and C# — BmMaj7 with the ninth added on top.
It sounds the same unease with more colour over it. The ninth softens the edge without resolving anything.
Minor tonic — melodic minor, extended.

| B | D | F# | A# | C# |
|---|---|---|---|---|
| 1 | ♭3 | 5 | 7 | 9 |
Also written BmM9, Bm(maj9) or B-Δ9. The same chord either way; which spelling you meet depends on who wrote the chart.
The same operation one voice further down: the third voice from the top falls an octave and becomes the bass.
That leaves a bigger hole under the top three notes, so a string gets skipped: the muted string in the middle is the shape, not a mistake.
BmMaj9 has 6 of them, on strings 6-4-3-2 and strings 5-3-2-1, from the 2nd fret up to the 10th — every inversion the chord has: B in the bass, D in the bass, A# in the bass and C# in the bass. The one to learn first is the A# shape at the 2nd fret.
4 of them sit on strings 6-4-3-2, so you can run the inversions up one set without changing strings — which is the whole reason to learn them as a family rather than as separate grips.
Five notes and four fingers, so something has to go. Keep D and A# (they fix the quality) and C# (what the symbol is about). Let F# and B go, in that order — a perfect fifth says nothing the root has not, and in a band the bass has the root.
Play BmMaj9 as a shell — root, third and seventh — and the spare string takes the 11 (E) or the 13 (G#).
All 7 common shapes as fret numbers, lowest string first. Hover or tap one to see it drawn.
How you get to it. The turn that lands on BmMaj9 is C#m7♭5 to F#7♭9: the ii and the V of B minor, which is where a minor tonic is usually arrived at rather than simply begun on.
Every note of BmMaj9 is in B harmonic minor and B melodic minor.
Change one note of BmMaj9 and you have Bmaj9 (the minor third becomes the major third), Bm69 (the major seventh becomes the sixth), Bm9 (the major seventh becomes the flat seventh), BmMaj7 (drop the ninth), BmMaj11 (add the eleventh) or Bmadd9 (drop the major seventh).
BmMaj9 is a minor chord — root, minor third, fifth. Minor chords on every root.
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.