Bobby Hill has been promoting — and DJing — jazz music in the Washington area for decades. (Bobby Hill)

It’s a warm Saturday morning in June, but the music decorating the air, the latest from pianist Satoko Fujii, sounds as delicate as snowfall. Moments later, Bobby Hill is sitting outside the studios of WOWD (94.3 FM) in Takoma Park, soaking up sunbeams, explaining his decades-long commitment to playing improvised jazz, like Fujii’s, on the local airwaves. “It’s a glorious, wonderful, powerful sound,” Hill says, “and people should hear it.”

Hill is celebrating his 40th year on the radio. He did four years as a student DJ at St. Mary’s College in Southern Maryland, 33 years at WPFW in the District, and is closing in on three years at WOWD, where his weekly show, “This! Music,” airs on Saturday mornings. And when he’s not broadcasting jazz, he’s presenting it on nearby stages. In 1997, Hill co-founded Transparent Productions, an all-volunteer promotion company that routinely attracts world-class improvisers to area listening rooms by routing every ticket dollar directly to the players. “I love these musicians, and I think they’re owed everything,” Hill says. “I love the music and I get to see music that may not otherwise be.”

His last four words feel especially well-chosen. Improvised music can only really exist in one place and time before it vanishes into the murk of history. Every note becomes a once-in-a-lifetime event. Hill knows how special that is, and as a listener, he considers it his payment. For the rest of our city, it’s a gift.

Shows: “This! Music” airs on Saturdays from 10 a.m. to 1 p.m. on WOWD 94.3-FM. Transparent Productions closes its 22nd season with two upcoming shows: Joe Morris and Tomas Fujiwara on June 8 at 8 p.m. at Rhizome, $20; and David Murray and Kahil El’Zabar on June 16 at 5 p.m. at Rhizome, $20.