It was an odd sight to behold: A sweaty audience jammed into the Rat, then known as Boston’s premier punk-rock club, to watch four musicians surrounded by a band of keyboards, pursuing some intricate and decidedly non-punk improvisations. Such was the scene in 1981, when Birdsongs of the Mesozoic quietly played its first gig. Two of the band’s musicians, Roger Miller and Martin Swope, were well-known as members of Mission of Burma, arguably the most popular and adventurous rock band in town. But Birdsongs was something else again: With the two Burma members changing instruments (tapelooper Swope played lead guitar in Birdsongs, while guitarist Miller switched over to piano), the all-instrumental band pursued chamber music, cartoon soundtracks, Eno-esque soundscapes, and everything in between.

Joined by accomplished organist Rick Scott and keyboardist Erik Lindgren — who is a garage-rock archivist, a successful writer of commercial jingles, and leader of the experimental band Space Negros — the band evolved a trademark sound over its first few years; always keeping a safe distance from conventional rock, but retaining enough tonal muscle to keep the Burma fans hooked. The first full-length album, 1983’s MAGNETIC FLIP, matched covers of Stravinsky (a shortened “Rite of Spring“) and the “Rocky & Bullwinkle” theme; plus adventurous original pieces that displayed a whimsy and lyricism seldom found in the avant-garde. Instead of club dates they’d do theater concerts, often accompanied by fanciful dinosaur films.

By this time Burma had split up due to Miller’s hearing problems, but an odd thing happened: On the 1985 EP THE BEAT OF THE MESOZOIC, the band had begun to approach the volume of Burma; live performances of the EP’s title track would find all four band members seated on the stage floor banging drums, hubcaps, and the stage itself. Rykodisc’s SONIC GEOLOGY CD includes the best material from the two EP’s and one album by the original lineup of the band.

With Roger Miller looking to form a new guitar band (No Man) and to perform solo shows, he left Birdsongs in 1988; saxophonist Ken Field came in and brought a heavier jazz influence, heard on the Cuneiform albums PYROCLASTICS and FAULTLINE. Both find the band rallying with Lindgren stretching out as a composer and Swope’s guitar coming to the fore. In 1991 Swope left as well, but the band again endured, bringing in guitarist Michael Bierylo. Though the original keyboard-driven sound has given way to a more coventional band lineup, the mid-’90s find Birdsongs still committed to pushing musical boundaries.