Just so you know, a sackbut is a medieval trombone; Big Sackbut is a three-trombone, one-tuba quartet, inspired in part by the groundbreaking World Saxophone Quartet. No drums, no piano, no nothin’ but bass horns. Like the WSQ, Fiedler and company swing hard without a rhythm section, moving between avant-garde and more mainstream sounds. Originals, such as “Mixed Bag,” provide solo space for all who avoid stepping on one another’s musical toes despite sharing the lower registers. They are rounded out by interpretations ranging from the salsa sans percussion of Willie Colon’s “Calle Luna, Calle Sol” to surprisingly restrained takes on Sun Ra’s “A Call for All Demons” and Captain Beefheart’s “Blabber and Smoke.” Zappa famously asked, “Does humor belong in music?” It’s answered here by the polyrhythmic: “Does This Make My Sackbut Look Big?” Innovative and fun.