It’s the kind of milestone you announce to the audience. “As of tonight, we’ve been playing for six months,” trumpeter and co-leader Joe Herrera proclaimed as the Bohemian Caverns Jazz Orchestra began its set at the titular club Monday night. D.C.’s only big band-in-residence has been a runaway success in that half-year, filling seats at the Caverns on a surprisingly regular basis—-surprising for the club as well as the musicians. A fine thing, but how far has it come in the musical sense?

What’s different:
The lineup, most obviously. New members incude Shannon Gunn and Corey Wallace on trombone (now a four-member section, expanding the band to 17 pieces) and Mike “Bags” Davis and Brad Clements on trumpet. The bass and drums were in flux at the beginning, but seem to have settled down into the powerhouse duo of Regan Brough and Dave McDonald. Amy Bormet still officially holds the pianist chair, but is currently on her honeymoon; Todd Simon is substituting.

That personnel change has reshaped the sound of the orchestra quite a bit. In its first two months or so, the saxophone section (still intact, by the way) was the focal point of the sound; now, perhaps because of its larger size, the trombones are the strongest force, often carrying the melody and sometimes overpowering when assigned the backgrounds. Also, Bormet tends to be the dominant rhythm player; Simon, though only a temp, is a much less forthright pianist, putting Brough at the rhythm section’s forefront.

It’s hard to say, though, whether this informs or is informed by the new arrangements in the band’s catalogue. Their book has grown exponentially, featuring the likes of Stan Kenton, John Fedchock, Maria Schneider, and Bob Florence and beefing up the Ellington and Basie repertoires. Impressive new setpieces of the night included Ellington and Strayhorn’s “Isfahan,” with alto saxophonist Sarah Hughes beautifully channeling longtime Ellington saxman Johnny Hodges, and the swaggering Florence tune “Carmelo’s by the Freeway.”

What’s the same:
Luscious, spit-and-polish ensemble playing. That the BCJO doesn’t rehearse is beyond belief when it coalesces so gorgeously on pieces like “I’ve Got A Crush On You,” which had no solos but was driven by beautiful group work on the saxophones, or the clever and fun arrangement of “All of Me” with the whole band supporting quasi-boogie-blues solos by Simon. This is a band of musicians who know the music intimately, and more impressively know each other almost as well. Perhaps they have the near-telepathy that so many of the great bands have described amongst themselves.

Another constant: premier soloists. There was great work to be heard all around, including a tasty staccato from Brough (“Blues for Red”), trumpeter John Williams with a dainty, happy line (“Carmelo’s by the Freeway”), and a bluesy strut on the same number by tenor saxophonist Elijah Balbed. The most potent solos, however, came from the alto and bari saxes. Brent Birckhead has a unique sound that demands attention to detail—-outwardly, his sound is broad and creamy, but upon close listen his tone betrays grit and razor-sharpness, whether in extended workout on “Blues for Red” or quick four-bar bursts as on “Fly Me to the Moon.” Baritone and co-leader Brad Linde, on the other hand, played lyrical and romantic in his featured solo on “The Willow,” with short, sinuous phrases that seemed to creep under the ensemble. And perhaps we should also mention Greg Boyer, whose yelping eruption on “Bebop Charlie” puts him high in the running for Most Powerful Trombonist on Earth.

The main thing that hasn’t changed in these six months is the consistency of the performances. BCJO is a high-caliber band that plays gorgeous music and has a million new directions up its sleeves, surely the reason it’s been able to keep audiences coming. That should include you.