Billy Sheehan may be the most influential rock bassist of the last 20 years. And throughout those years, he's favored the signature instruments he co-designed with Yamaha's custom shop.

Unlike many of the players who mimic his fretboard pyrotechnics, Sheehan has always balanced virtuosity with solid songwriting and supportive rhythm-section playing. Evidence: his work with Talas, the David Lee Roth Band and on solo albums like his most recent, Cosmic Troubadour, which also highlighted Billy's guitar and vocal skills.

It was never my goal to become technical. I just wanted to play the cool stuff I heard in my head.

Sheehan recently called from Sofia, Bulgaria, where he was on tour with another David Lee Roth Band vet, guitarist Steve Vai.

What first inspired you to expand the technical boundaries of electric bass?

It was never my goal to become technical. I just wanted to play the cool stuff I heard in my head. I'd hear a string of notes played on some instrument and try to figure out how to do them on bass. I don't read music. I don't know theory. I just have an intense, ongoing love of playing.

Your best-known innovation is two-handed tapping. Is that technique still part of your sound?

A bit. I'd shied away from it for years because it became cliched. I purposely went the other way. Every time my right hand started to reach over for the neck, I'd stop myself. That forced me to invent more ways of playing that didn't have anything to do with tapping. But in the last few years, I've revisited some of the things I've done over the last few decades, and I've been returning to tapping in a refreshed way.

Despite your virtuosity, you usually play four-string basses.

Yeah. Once in a while I'll go to a six-string. I figure, if I'm going to start adding strings, I might as well go right to six and skip the five! [Laughs.] But I grew up on the four-string, and I'm a creature of habit. I just love the feel of a four-string in my hand. Besides, it's a myth that five- and six-strings are harder to play. They're not--they have the same patterns and notes. I did play a six-string bass on "Just Take My Heart," a Mr. Big ballad. But I wound up performing it on four-string, by dropping the low E string to D.

How did you start working with Yamaha?

They contacted me 20 years ago when my band, Talas, started to make a little noise. I was honored. I'd known about Yamaha basses for years and I knew they made superbly crafted instruments. The first bass we came up with was part of the BB Series, and later we developed the Attitude series. We've made several other models, but I still gravitate most toward the ATT LTDII. It's a P-style bass, but with some unique features, like a more solid neck joint than the one on vintage basses. I often bend the neck for vibrato, and I always used to knock the necks out of alignment. I've also added an extra fret so you can go up to high E instead of an E-flat, which is handy because most rock tunes are in E. And it has dual outputs, which all my instruments have had since 1971 when I chiseled out a hole in my bass to add a neck pickup. My mom had to vacuum up the chips off the living room floor! I've always used two amps--one does basic bass and the other is the frosting on the cake. That way, I never lose the cake in favor of the frosting, because there's always one amp covering the low end. When I start playing high notes, it doesn't sound like the bass player went away.

What's coming up for you?

My band, Niacin, has a new record called Organic. The group is a trio with John Novello on organ and Dennis Chambers on drums. Dennis has been one of the most influential musicians in my life. He's the Hendrix of drummers, the best musician I've ever worked with on any instrument, period. We'll be doing some shows this summer. I also have two new instructional DVDs. One's for absolute beginners, and one's for more advanced players. I try to relate some of the things I've learned over the years--not so players can be clones of me, but to give them the tools to make their own voices. Doing these DVDs was a way to sum up some of the questions I receive from players. I answer all my email, thousands of letters, and try to give the best advice I can. I'm humbled and thankful that I've had any success at all. If I can help another player out, I'm very glad to do so!