WHEN the late Mary Lou Williams (below), a pioneering jazz pianist, composer and arranger, had her own weekly radio show in 1945, she’d introduce the broadcasts with a semi-improvised piece.

For what would have been her 96th birthday tomorrow (she died in 1981), the Williams collective – featuring pianist Geri Allen, bassist Buster Williams and drummer Billy Hart – will reinterpret 12 of these short works tonight through Sunday at Iridium (1650 Broadway, at 51st Street; [212] 5822121). Two sets nightly at 8 and 10, with an additional 11:30 p.m. show tonight and tomorrow.

Tickets are $27.50 and there’s a $10 minimum per person.