After years of being infatuated with Yeats's poetry, local songwriter and storyteller Joseph Daniel Sobol has finally compiled a theatrical cycle of songs and spoken pieces set to the Irish master's verses and essays. Titled In the Deep Heart's Core: A Mystic Cabaret and intended to be performed cabaret style, the work features 19 of Yeats's poems that Sobol regards as particularly folksy, mystical, and moving. For each he's come up with an appropriate musical accompaniment, from ballad to jazz riff to Dowland-like lute song. But folk and Irish traditional elements of course saturate this impressionist, drama-laden collage, meant to conjure up Yeats's romantic yearnings and disillusionment, his political musings, and his unrequited love for Ireland. Still a work in progress, the cycle will be premiered by the vocal trio of Sobol, Tom Orf, and Kathy Cowan, whose radiant, vibrant voice has earned her the reputation of best interpreter of Irish songs in town. The crackerjack band consists of Sobol, bassist John Floeter, violinist Gerry Field, and keyboardist Elizabeth Falcone. Saturday, 8 PM, Second Unitarian Church, 656 W. Barry; 549-0260. Sunday, 3 PM, Irish American Heritage Center, 4626 N. Knox; 282-7035.