A sobbing long tone on the fiddle and a tender strum of the guitar are all Martin Hayes and Dennis Cahill need to woo anyone with a modicum of interest in traditional Celtic sounds. For the past 20 years, the two masters have refined an enviable chemistry, the kind of deep teamwork that makes their airs, reels, and jigs seem simultaneously designed and offhand. Perhaps it’s odd, then, that they celebrate their partnership by inviting a series of comrades to the stage. For eight dates in September they hold forth with one player per night, and the guest list stretches from the New Yorker’s poetry editor (guitarist Paul Muldoon) to Uilleann piper Ivan Goff, and at least two wildcards, local hero Doveman (spectral pianist Thomas Bartlett) and jazz clarinetist Doug Wieselman (last seen at Sunny’s in Red Hook tearing it up with Smokey Hormel’s cha-cha outfit). Longtime devotees needn’t fret: chances are slim that any of the intriguing interlopers could cloak Hayes and Cahill’s abiding communion.

Fri., Sept. 20, 8 p.m.; Sat., Sept. 21, 8 p.m.; Sun., Sept. 22, 8 p.m.; Thursdays-Sundays, 8 p.m. Starts: Sept. 20. Continues through Sept. 29, 2013