Those who attended the latest edition of former Band drummer Levon Helm's "Midnight Ramble" house concerts — typically sold out at $100 a ticket — were simply left shaking their heads.

Helm for his semi-regular concert Saturday welcomed two surprise guests — Elvis Costello and New Orleans composer, singer and pianist Allen Toussaint, an anchor of that city's music scene.

Costello played acoustic guitar but did not sing for a good part of the evening. He played none of his hits and looked like a rumpled college professor late for class. But he was obviously very pleased to be playing Helm's sideman on songs he was learning on the spot.

When Costello did sing, he stopped the show.

Costello and Helm's band members discussed chord progressions and keys of songs seconds before launching into a tune. But Costello never seemed to miss a beat and maintained that suave, debonair air of a showman that is a linchpin of his on-stage persona.

New Orleans style

Toussaint, an old friend of Helm's who worked with The Band, joined in well into the set, tickling out of the ivories some hard-core Crescent City Dixieland that brought the crowd to its feet. His style of music was deep like the Delta and combined classical, gospel and Motown into a melange that is perhaps rarely heard so far north of the French Quarter.

Through it all, Helm sang, played guitar, mandolin and drums. He rarely stopped flashing the blinding grin of a child who had just pulled off a schoolyard prank.

Costello's star power radiated when he assumed leadership of the ensemble and took over lead vocals.

One highlight was the preview of new material that he and Toussaint recently recorded. In fact, that collaboration played a big role in bringing the two to Helm's studio.

After Hurricane Katrina struck New Orleans, Helm sent his old friend Toussaint a bouquet of flowers. Fast forward several months and Helm gets a call from Toussaint saying he would be in New York working with Costello and the two have some time available to come to Woodstock.

"My long-time, dear friend," a gushing Toussaint said on-stage about Helm. "I'm so glad to be in his neck of the woods ..."