If adjectives had faces, “irrepressible” would wear the grinning countenance of soul man Alvin Cash. Cash’s “Twine Time” on Chicago’s Mar-V-Lus label launched a major dance craze in the mid-60s, although his contribution to the tune consisted mostly of shouting hoarse imprecations over his backup ensemble’s funky R & B riffing. He never scored that big again, but subsequent efforts–“Barracuda,” “Philly Freeze,” “Alvin’s Boo-Ga-Loo,” “Keep On Dancing”–entrenched his reputation as a major figure in the development of 60s-era black popular dance. Cash hasn’t had anything approaching a hit for almost 30 years, but you’d never know it to see him in action: he’s managed to sculpt an apparently endless career for himself using little more than unquenchable faith in his own legend. He’ll show up unannounced at someone else’s gig, take the stage, and start dancing alongside the headliner; his self-promoting birthday parties and tributes have become urban folklore on the south side; his stage act remains a combination of hyperkinetic patter, shouted dance instructions, and the occasional blues standard. However unlikely the setting and no matter how faded the glory, when Cash takes the spotlight and launches into his routine it’s 1965 again, and it’s star time at the Regal. Tuesday, 9 PM, Koko Taylor’s Chicago Blues, 7 W. Division; 337-2583.