It’s a Sunday night at the AllWays Lounge, and Dr. Sick and the Late Greats jump on stage with a vigor that gets everyone dancing from the very first tune.

Performing traditional jazz songs with the same baffling ease as waltzes, they deliver a varied repertory with great confidence and passion.

“We always play songs that others forget to play,” violin player and singer Dr. Sick said between songs before embarking on a fantastic gypsy-rock version of Bessie Smith’s “Devil’s Gonna Get You.”

Dr. Sick, a multi instrumentalist more often than not found sawing away on his violin, performs with many different musical outfits, often accompanied by a selection of burlesque performers.

With the Late Greats, the band keeps the swing going the entire concert, slowing down abruptly before quickening the beat gradually, and it’s not rare to have dancers almost running when a song reaches its end.

Which the band is completely aware of.

“This next song, we call it ‘challenge to the dancers’” Dr. Sick said. “It’s like a rollercoaster in a song.”

Stomping and swinging, the joy and energy coming out of the band are utterly contagious. There is something intensely strong in the way people connect to the music, from crazy swing lovers to this old Greek woman who could not be happier when the band played a traditional Ukrainian tune two weeks ago at the Spotted Cat.

It’s half past eleven by the time the band finishes its second set with an outstanding and completely innovative version of “Can’t Take My Eyes Off Of You.”

It’s “a true story,” as Sick likes to mention at the end of pretty much all of his songs.