Jack Jeffers, a largely self-taught, all-around bass trombone and tuba player who composes, conducts, contracts studio musicians, perform in Broadway pit orchestras and jazz bands, and for the last eight years has led his own N.Y. Classics Big Band. Jack Jeffers doesn’t call his collective the New York Classics for nothing; you’ll have no trouble recognizing pieces such as Ellington’s “Mood Indigo,” Mingus’s “Goodbye, Pork Pie Hat” and Jobin’s “Corcovado.” He’s been in solidarity with avant-polymaths like drummer Warren Smith and Rahsaan Roland Kirk’s pianist Sonelius Smith for more than three decades, which explains why Jeffers’s soloists tend to come at both the familiar tunes and his originals from an inventively off-kilter base.