David Letterman and Paul Shaffer end their long weeknight run

If not for his five years in the “Saturday Night Live” band, Paul Shaffer might not have been on David Letterman’s radar.

The wry music director for both of the host’s late-night shows – first on NBC, then on CBS – also participated in some “SNL” sketches during his tenure there (1975-80), so when Letterman went looking for an all-purpose on-air comrade, Shaffer got the call. Their weeknight partnership of more than three decades concludes when the longest-running host in late-night history ends the almost 22-year run of “Late Show With David Letterman” Wednesday, May 20, on CBS.

Shaffer has done many other things, such as being the musical director for the Rock and Roll Hall of Fame induction ceremony since its inception, and he allows “it was all because of my association with Dave. When they called me for this, they did say, ‘ We want somebody that Dave can play off of.’ I don’t know if they ever said ‘sidekick,’ but I said, ‘I’m that guy! Yes! I could!’

“I had gone from being a writer of musical material to a person who did some performing,” Shaffer says, “and in fact, Dave had seen some of my stuff on ‘ Saturday Night Live.’ They never really encouraged (Shaffer-inclusive comedy bits) once we were on the air; I just had to sort of start doing it.”

Shaffer recalls a story that he notes Letterman tells “with a great deal of irreverence, but it’s absolutely true. We were doing a sketch early in our run at CBS where I was going to put a bag over my head, but they would switch me with a dummy and then he would whack the head with a baseball bat. Well, I was sitting there for real, and he had the bat ... and he was going to take a whack. And he just thought better of it. He shudders when he thinks of it, because he really could have put my lights out.”

On a couple of occasions, Shaffer was asked to fill the main “Late Show” seat, once when Letterman was ill and once when he was absent for the birth of his son. “There’s nothing like sitting in that chair and having the whole weight of the show on you,” Shaffer attests. “My job is a breeze compared to that, but when we go to a commercial break, that’s when I go into action playing for the studio audience. I have to concentrate for a full hour, but one out of 24 isn’t so bad.”

With Stephen Colbert set for a September debut on “Late Show” – which has won 16 Emmys – Shaffer is appreciative of the loyalty Letterman has shown his staff, encompassing such other long-timers as executive producers Barbara Gaines, Jude Brennan and Rob Burnett. The chance to cross paths with so many music greats has, expectedly, been a particular bonus for Shaffer.

“I’ve been thinking about it as we get nostalgic towards the end,” he reflects, “how Eric Clapton was one of the first guys to sit in with our band all night, and then everybody wanted to do it. I got to do Live Aid because (co-organizer) Bill Graham saw me on this show. I can thank David and the show for all these great experiences.”

And as for the future? “I have absolutely no plans,” Shaffer says. “All I know is that I want to keep playing the piano, because that’s my first love. I love to do comedy and I love to do music, but I don’t think I’ll ever get to do them at once again like I have for Dave.”