It wasn’t easy to silence the set of “Saturday Night Live,” which at Friday evening’s rehearsal was a cacophony of banging hammers, buzzing saws and chattering crew members, but Steve Martin did it with a banjo.

On the main stage of NBC’s Studio 8H in Manhattan, wielding a Gibson Florentine from the 1920s and accompanied by a quintet of bluegrass musicians, Mr. Martin was plucking, strumming and, yes, singing his way through an original song called “Late for School,” about a young delinquent racing to beat the tardy bell. The hoedown brought the room to a halt, and when it was over even the surliest stagehands couldn’t help but stand and applaud.

In his mercurial career Mr. Martin, 63, has gone from manic, rabbit-eared stand-up comedian to introspective memoirist. He has made movies for Carl Reiner (“The Jerk”) and David Mamet (“The Spanish Prisoner”) alike. Through his many incarnations a banjo has never been far from his reach, whether the instrument was an integral part of his act or a tool to help him unwind in private.

Now Mr. Martin is once again in the musician’s role as he releases an album called “The Crow: New Songs for the Five-String Banjo.” The record (which is being sold exclusively on Amazon.com, until April 26, when it also will be released elsewhere) is a token of his affection for bluegrass, with appearances by performers like Vince Gill and Dolly Parton. But it is also an opportunity to show off one of his less celebrated, least commercial skills, and to reimmerse himself in a musical genre he never fully gave up.