When audiences come to see Michael Hedges in concert for the first time, they often are surprised to hear him sing. After all, his first two albums for the pastoral folk/jazz Windham Hill label were devoted exclusively to acoustic guitar instrumentals. With his unorthodox tunings, hammer-ons, pull-offs, tapping and bell-tones, he had established himself as a leading innovator on the steel-stringed guitar.

In concert, though, he intersperses his pioneering instrumentals with original songs and songs by his heroes -- Neil Young, Joni Mitchell, John Lennon, Bob Dylan and Willis Alan Ramsey. His own songs strike a balance between his radical guitar technique and the intense introspection of these heroes.

Just this week Hedges' vocals became available on record for the first time -- on his third album, "Watching My Life Go By." He will perform both those songs and the instrumentals that made his reputation when he appears with pianist Liz Story at Lisner Auditorium tonight.

"Yeah, audiences were often surprised that I did the vocal stuff, too," Hedges says. "But that made me glad, because I always like to surprise people. If I keep playing the same tunes in the same style, I'll end up repeating myself, and that's against my philosophy. Once they get used to this, I've got some other stuff up my sleeve to keep them surprised."

Though he grew up in Oklahoma, Hedges came of age musically in Baltimore. It was there that he studied guitar and composition at the Peabody Conservatory. While he was studying Be'la Barto'k and Anton Webern in school, he was taking private jazz guitar lessons from Larry Woolridge and playing Young and Mitchell songs in Fells Point bars. This unusual combination of influences helped shape his distinctive sound: lovely folk melodies played in cyclical progressions but with modern art music harmonies and jazz inversions.

"I've been writing songs ever since I was playing the bars during college," Hedges says. "I didn't sit down after my two instrumental albums and say, 'Now I'll write a vocal album.' I wrote all these songs concurrently with the instrumental pieces. The oldest piece on the album, 'Running Blind,' was written seven years ago; the newest piece, 'Face Yourself,' was written as I was finishing up the second album.

"Just the same, I'm glad I waited this long to record the songs, because I don't think I had the vocal ability to do justice to them before. I feel like I've just come into my own as a singer."

Hedges credits two teachers in particular for his new vocal maturity. One was his father, now a speech therapist at California State University at Fresno. They spent one session just on consonants, and after several such sessions, the son's confidence was markedly improved.

The other teacher was jazz vocalist Bobby McFerrin. "I first heard Bobby at the Great American Music Hall in San Francisco," Hedges recalls, "and he so impressed me that I called my wife at intermission and told her to get in a cab and get over there to hear the rest of the show. He's a very spiritual man -- did you know he once started to be a priest?

"His concentration is almost absolute; that's why I was drawn to him, because I want to be similarly organized. So I weaseled his phone number from Darol Anger and asked him if he would give me lessons. We did a few exercises, but we spent most of the time talking about what we're thinking about when we sing. He taught me that the main thing is to know what I want to say and why I want to say it. Once I know that, I can forget it all and just do it."

When Hedges called McFerrin one day and heard one of his own guitar pieces on the answering machine, he figured it was okay to ask McFerrin to contribute to the new album. The result was a tour-de-force scat solo on "The Streamlined Man."

Another key connection for Hedges' new album was producer Elliot Mazer, best known for his work with Neil Young. After reading a cover story about Hedges in "Guitar Player" last February, Mazer called Hedges up and offered to produce the vocal album. Hedges was delighted.

"I played Neil Young's tunes for so long in the bars," Hedges explains, "that I felt intimately acquainted with those recordings that Elliot produced. I knew he could get that live performance sound I wanted. We worked out a deal with Windham Hill where they gave me money to buy recording equipment to build my own studio instead of buying time in another studio. Elliot handpicked all the equipment for me, and he and I built the studio in a garage in Palo Alto [Calif.]. He went beyond the call of duty."

Now that the vocal album is done, Hedges has several other projects under way. He took his first record royalty check and bought four electric guitars he had his eye on. After several years of practice, Hedges is about to unleash his electric guitar playing on an unsuspecting public. The first hint of things to come was a strong, humming electric guitar solo on the new album's "I'm Coming Home."

He has also bought two Dyer harp guitars -- strange, mutant acoustic instruments from the 1920s that have a normal six-string fret board plus five extra bass strings strung across an arching sounding board above the neck. Though the harp guitar was designed as a strumming instrument, Hedges is inventing his own technique for playing it as a solo instrument.

"I have to keep moving," he says. "I have to keep evolving so I don't die. The worst thing that could happen to me would be to get bored."