There are musical and economic advantages for the singer who performs old blues and folk songs on acoustic guitar. The old songs still hold immense power; almost everything valuable about American music can be traced back to them. Moreover, there is no expensive equipment to buy or haul, and no paycheck to divide.

Both motivations fueled the American folk boom of the early '60s, and the recent folk-music boom as well. An exciting new generation of folk singer-songwriters has emerged: Steve Forbert, the Roches, Willie Nile, George Gritzbach, Ralph McTell, Chris Smither, George Gerdes, Willie Tyson Bryan Bowers and more. With the first flush of success, though some are rushing into the embrace of electronics.

Steve Forbert has been one of this generation's most exciting and successful performers. He made a delightfully Dylanesque debut in 1978 with "Alive on Arrival (Nemperor 33538). Though Forbert played old folk-blues tunes in clubs, the record skipped right past that stage to 11 original folk songs. The occasional electric guitar and bass were merely ornamental. The essence of each song was Forbert's acoustic guitar plucking, harmonica tooting, wispy singing and understated lyrics.

Forbert's recent follow-up album, "Jackrabbit Slim" (Nemperor 36191) is a quick rush into folk-rock. Nine of the 10 songs are given full rock 'n' roll band arrangements. It's too quick a rush. Though some songs gain in power from the added backing, many lose the subtle intimacy of Forbert's solo performances.

The economic motivation for the quick jump from solo folkie to rock band is obvious; "Romeo's Tune" from the new album was an unexpected hit single for Forbert. The musical motivation is less obvious. Forbert has a very soft voice. Too often on the second album, the fragile drama of the voice is lost amid the thrashing electronic backing.

Willie Nile's Washington debut at the Cellar Door last May was a powerful solo acoustic performance. Like Forbett, Nile applied classic folk forms to his own sharply sculpted lyrics. However, Nile's first record, "Willie Nile" (Arista AB 4260) jumps directly into full folk-rock arrangements. Only one of the 11 Nile originals is given a solo acoustic performance.

It's regrettable the acoustic side of niles music hasn't gotten more exposure on record. But the electric folkrock side is impressive enough by itself. Nile has a much better senses of catch melodies and rock rhythms than Forbett. "That's the Reason" has a genuine Buddy Holly bounce, and "It's All Over" has a chorus so catchy it could have been an early Beatles tune.

The price of sticking too closely to acoustic folk-blues is illustrated by George Gritzbach. "The Sweeper" (Kicking Mule KM 304), the second album by the Cape Cod singer-song-writer-guitarist, was one of the best records of 1979. If you never heard of it, you're hardly alone, for the small-label release had little distribution and less publicity. Gritzbach shares the fate of most acoustic, traditional performers who are confined to small, underfinanced companies.

Gritzbach has followed a slower evolution than Forbert and Nile, and it may pay off for him in the long run. "The Sweeper" contains four traditional blues tunes and five totally solo performances. The other songs features sparse, acoustic accompaniment. The guitar licks that Gritzbach learned personally from Reverand Gary Davis and from the records of Robert Johnson give his music a technical quality that Forbert's and Nile's lack.

Moreover, Gritzbach may be the best songwriter of the three. "The Sweeper An' the Debutante" is reminiscent of Randy Newman's short-story songs about American eccentrics. And Gritzbach's tale of cross-class seduction in a hotel is loaded with irony and humor.