When it comes to the blues, only the rarest of musicians can win. White performers have to cope with complaints about their suspect genes, and most white musicians who begin as blues interpreters are soon mixing their sound with other, less esoteric influences -- often to great financial (and sometimes artistic) success. And for years now, those blacks who cared to serve an apprenticeship to the blues have found themselves bound to a limited audience, playing the same tired runs to the same crowds. Meanwhile, purists moan that a new Muddy Waters or Robert Johnson -- a blues version of the Second Coming -- is a foggy possibility at best.

Two interesting new records, one by a white blues group, the other by a black artist being hailed as the closest thing to a modern blues master, provide some insight into what happens when blues are used -- or left behind -- to make it in contemporary times. Cranstons have been gaining a reputation by steady touring, three good records, and the fact that the ultimate white-rip-off-of-black-music band, The Blues Brothers, recorded the Cranstons' "Excusez Moi, Mon Cheri." With "Up From The Alley" (Waterhouse 10), the band's direction has moved decisively away from a blues-band format. Though Pat Hayes still supplies a sizzling harmonica, and one song is a Sonny Boy Williamson composition, there is a diversity here that spans rock 'n' roll, rhythm and blues, rockabilly and the modern drink-along eclecticism that encompasses all these forms. And to dispel all doubts of a willingness to dabble in the more commercial realms, we have "Keep On Driving," a song that lifts Bruce Springsteen's themes and melodic urgency while finishing with a double guitar lead that would sound at home on a Marshall Tucker record. A fine pop song, but it's unlike the rest of "Alley," which lends an appealing Midwestern openness to the good-time funkiness and matter-of-fact cacophonies with which we associate Southside Johnny. There's a lot of fun here, delivered with wit and punch.

The only problem is some low fidelity in the recording process. It may or may not be the fault of Del's Tire Mart of Minneapolis, where the record was made, but at times it sounds like Lamont Cranston was indeed performing in the alley, but being miked from upstairs. Once the songs draw you in, and you crank your home sound up, however, you hardly notice.

While Lamont Cranston may one day get the widespread attention they deserve, Son Seals all but owns his critics. As a black man expertly playing "pure" amplified blues, Seals is touted as contemporary successor to past legends -- the Great Black Hope of the blues. With all this acclaim, he has yet to reach a mass audience, and, perversely, this failure is cited as further proof of his authenticity: He'd rather play the blues than make a mint.

"Chicago Fire" (Alligator 4720) is promoted as another step in Son Seals' continual "search for the new blues." Still, Seals sticks to traditional forms here. His strengths are his voice and guitar. The notes that he wheedles and coaxes from his exquisitely toned Guild are gruff, steady, spartan in their brevity. Meanwhile, his singing is chesty and macho, but capable of firm irony.

Highlights of this fourth record by Seals include an understated, mournful guitar introduction to the slow "Leaving Home"; a booming vocal that interacts with King Solomon's nervy piano on "Crying Time Again"; and a promise to "play some blues for you" on "Buzzard's Luck" that he keeps memorably. A nagging problem throughout the record, though, are the trite horn arrangements, which too often bog down the action.

Seals is obviously accomplished in his field, and "Chicago Fire" is proof.

But to take this record as evidence, one would have to conclude that attempts to induct Seals in a blues Hall of Fame are premature at best. His songwriting here, and to a lesser degree, his musicianship, does not create the transcendent highs that the very best of blues provide. Its very power prevents "pure" blues from reaping huge commercial rewards -- a mass audience will seldom subscribe to a truth so undiluted that it seems to rise out of madness. Son Seals has some soul-shattering heartbreak to reap before he reaches those extremes, and if he ever does, he still won't be going platinum. But that's what the blues are all about.