Caleb landed his first big touring gig with soul/funk songstress Nikka Costa in late 2000 during her career peak; after that he joined funk diva Macy Gray’s tour. Having proved himself on the road, the 33-year-old has now earned a reputation as a legit R&B session player, working with Justin Timberlake (“Damn Girl” from JT’s FutureSex/LoveSounds), and writer/producer Will.i.am. Meanwhile, Speir has racked up writing credits with Will.i.am on “Pose,” a FutureSex/LoveSounds bonus track, and “Coming Back to You,” a Macy Gray tune from the Denzel Washington movie Déjà Vu. Caleb also co-wrote four of the tracks that make up Gray’s new release, BIG.

You’ve established yourself as a talented player in Macy’s live band. Was it easy to transition into studio work?
Even if people are confident in you as a tour musician, you really have to earn your stripes in the studio. When Macy started working on her new record a few years ago, I had done some work on the early demos but had never been asked into the studio; I hadn’t done any professional recording. Then she invited me to stop by one day. I brought my basses just in case, and within five minutes of meeting Justin—who was producing a song—I was recording. It snowballed from there. It led to playing on Macy’s record and working with Justin on his.

What have you learned from working in a studio environment?
I haven’t been recording long, but I’ve learned you have to be consistent and keep a groove, and that’s not always easy. Sometimes there’ll be lots of people hanging around—the artist, producer, engineer, friends—and they’re all waiting on you to come up with a part. It made me nervous at first, but after a while, you get to a place where it doesn’t matter who’s in the room. It’s weird—live, playing in front of thousands of people doesn’t make me nervous. Being in the studio with people waiting for you to lay down a part requires some adjustment.