A jazz octet falls into the gray area be-tween small and big band, and Jonathan Parker’s octet behaves like the latter. The piano, bass, drums, and rhythm section are joined by five horn players (including Parker, who plays alto and soprano saxophones, as well as the flute), begging for elaborate interplay and orchestrations. Accordingly, Parker’s debut album Interloper is, first and foremost, a showcase for the local leader’s writing in both arrangements and compositions. Lucky for us, that writing happens to be superb.

It’s also quite ambitious. Parker gives notice of his big ideas with the opener, “Clearyisms.” The tune has two iterations of its introduction, followed by a horn melody with a complex form (AABACA) and even more complex chord voicings. It’s heady stuff, and Parker proceeds to top it with “Jim,” a long composition with separate melodic sections for flute, soprano sax (both by Parker), and trumpet (Dave Chisholm), then a final section for trumpet and soprano together—not counting the dense obbligatos that come in under Chris Pattishall’s piano solo or the full-ensemble variation of the theme near the end. And that’s just the first two of Interloper’s seven tracks; the extraordinary writing for bass clarinet (played by Owen Broder on “Tranquility” and Bill Mulligan on the closing “Lament”) hasn’t even come in yet.

All the ambition in the world means little, however, if the music isn’t inherently compelling, and Parker is more than up to that task. Sure, melodies like “Jim” are compounds, but the component parts are simple and full of memorable hooks. (Some of the most memorable in jazz history, in fact: The theme of “Gage” is ultimately a long build-up to and comedown from the opening lick of John Coltrane’s “Giant Steps.”)

Still, they can be deceptive, as on the record’s best tune: “Tranquility,” written by bassist Curtis Ostle but arranged by Parker. It begins with a slow, dark, through-composed harmony line for Parker’s flute, Chisholm’s trumpet, and Paul Jones’ tenor sax, over the drone of Broder’s bass clarinet and Peter Nelson’s trombone. After 40 seconds—just long enough to wonder if this is all the whole track will sound like—Pattishall and Ostle, followed by drummer Alex Ritz, bring in a swinging groove to drive the tune’s intoxicating, hummable melodic phrases. (Those grooves are not to be underestimated, either: From beginning to end, whether in 4/4 time or the 6/8 of “Jim,” Interloper swings its head off.)

Improvisations, while not Interloper’s top priority, are nonetheless high-caliber. Chisholm makes a particularly fine contribution on “King of the Hill,” starting with the four-note hook from the written theme and making it the springboard for a long charge. (Pattishall precedes him with another great solo, attacking Count Basie licks with aplomb.) Broder, meanwhile, tiptoes into “Gage” with a gorgeous, subtle baritone sound and discrete phrases that are sometimes stock, but he makes them work. Even Ostle does exquisite work on bass (“Sundown,” “Tranquility”). Interestingly, though, Interloper’s weakest solo is the leader’s, a soprano entry on “Jim” comprising arpeggios and easy licks. But Parker ably compensates with his gifts as a writer and bandleader. A team of eight can make a big splash.