As an actor (in numerous plays at Steppenwolf, Remains, and other theaters, and in the forthcoming film Singles), Jim True knows that the key to words isn't just what they mean, it's how they sound--their assonance, alliteration, rhyme, and rhythm. Those are the elements True explores in his work as a composer; his texts include poems and monologues by Dylan Thomas ("And Death Shall Have No Dominion," "Youth Calls to Age"), William Butler Yeats ("I Am of Ireland"), E.E. Cummings ("When Faces Called Flowers"), and Michael Cristofer (a letter from a woman to her dying mother from the play The Shadow Box). His collaborators are guitarist Michael Smith and accordionist-pianist Willie Schwarz (both of whom worked with True on Broadway in Steppenwolf's The Grapes of Wrath), so it's no surprise that the music for this "late night poetry concert" is folkish and Celtic-flavored; Jethro Tull, Van Morrison, and Bob Dylan are among the recognizable influences. Bassist Larry Gray completes the quartet assembled for this unusual fusion of tunes and text. Tonight, Thursday, and next Friday, December 20, 11 PM, Steppenwolf Theatre, 1650 N. Halsted; 338-1650.