AT HIS BEST, Billy Joel is known in the music world as a talented keyboard artist who sings moving ballads. Joel got that image with the release of Piano Man, his debut album on Columbia Records, which followed a virtually unknown and very rare release called Cold Spring Harbor. The title track from Piano Man, along with other slow ballads such as "Captain Jack" and the more upbeat "Ballad of Billy the Kid," created the in age for Joel, and he has continued it with songs such as "Miami 2107" and "I've Loved These Days."

Yet in The Stranger, Joel's latest release, the native Long Islander who mentions New York in almost all his songs appears to be telling the world that he can do more than just coast through slow, moving ballads. He already hinted at that hidden diversity on the Turnstiles album with a bluesy tune called "New York State of Mind" and upbeat rockers such as "All You Wanna Do Is Dance" and "Say Goodbye to Hollywood." The last song overflowed with the famous heavy Phil Spector drumbeat that pervaded the rock of the '60s.

The title track on this newest album tells about the hidden side of Billy Joel. As the lyrics suggest:

Some are satin some are steel

Some are silk and some are leather

They're the faces of the stranger

And we love to try them on

Trying on these new faces is what Joel's new album is all about. From the traditional storyteller to the disco rocker to the gospel vocalist, Joel plays many roles as he experiments with differing styles of music.

Interestingly enough, the four cuts on side one, all of which have received considerable airplay on both the AM and FM dials, are the least innovative songs on the album. They fit neatly into the pattern that Joel has established in his past releases, but their success is still a tribute to the freshness and originality Joel brings to each of his new songs--even the ones that most resemble his familiar ballads.

"Movin' Out" leads off the album with an upbeat rocker that, as the album's first single, did not do well. It is a coarse song that ends with the revving of a motorcycle engine as the music fades away and hardly ranks as one of Joel's best releases. It is balanced out, however, by the blockbuster of the album, "Scenes from an Italian Restaurant,"

Because of its seven-minute-plus length, this song will probably never break open the AM charts ("Stairway to Heaven" is one of the few songs that ever made the rise to fame despite a more-than-seven-minute duration), but the song stands out as an example of Joel's tremendous talent as a vocalist/instrumentalist/composer. From the slow, ballad-like start to the well-rhythmed second section, to the rapid, light-rock middle of the song, Joel controls all the elements of his music as he reminisces about high-school days. Amidst a superb clarinet melody and the fantastic saxophone that Richie Cannata always adds to Billy Joel's music, "Scenes from an Italian Restaurant" remains brilliant.

In the popularity polls, though, "Italian Restaurant" cannot match "Just the Way You Are," a sentimental throwback to his earlier "You're My Home." Each time Joel performs the current hit single on stage, he quiets the screams of even the Long Island fanatics who support their hometown hero. In silence, his listeners delight to lyrics such as:

I said I love you and that's forever

And this I promise from the heart

I could not love you any better

I love you just the way you are

The song's sincere appeal to simplicity has won the hearts of listeners who have boosted the song well up into the Top 40 charts. With the gentle Fender Rhodes playing background to a pair of soft acoustic guitars, Joel has put together a tune that succeeds because it is so straightforward.

Yet for all the popularity of side one, the album's second side has remained obscure. For six years, Billy Joel has been turning out superb music that has gone relatively unnoticed, and the success of the four cuts on side one of The Stranger is a first for him. It seems that the listening public has now accepted the Billy Joel who has been around for years, but they are not yet ready to accept his new experiments--or as he calls it, "a face that we hide away."

Side two is the exposure of Joel's hidden talents, his tremendous creative ability. Though much of the side is not of as high caliber as the material on side one, it is remarkably diverse. Probably the weakest cut of the side is "Vienna," a bluesy lament filled with the sounds of Dominic Cortese's accordion, which still does not compare to "New York State of Mind," the blues entry and consistent show stopper from Turnstiles.

Joel turns to a bit of R&B in the tradition of Stevie Wonder with "Get it Right the First Time," using a flute to accentuate a strong piano line. His catchy refrain is almost a direct outtake from the first two lines of Wonder's "Another Star."

The side's strongest entry is "Everybody Has a Dream," a gospel tune complete with a slow moving vocal and a heavy organ instrumental part. The song even has a gospel chorus that includes singer Phoebe Snow.

The side's other two cuts, "Only the Good Die Young" and "She's Always a Woman" don't quite come together, although the first one features a strong set of lyrics. The song starts off with:

Come out, Virginia. Don't let me wait

You Catholic girls start much too late

But sooner or later it comes down to fate

I might as well be the one.

"She's Always a Woman" has a bright arpeggio guitar part in the background, but the song lacks the vitality that comprises so much of Billy Joel's work, and never goes anywhere.

Why The Stranger has suddenly earned Billy Joel the airplay he has lacked in the past is a mystery, especially to his long-time fans. The Stranger is a solid album with a particularly good first side, but it is certainly no stronger than Turnstiles, and not nearly the phenomenal collection of songs that made up Piano Man. Still, with a second consecutive solid album (after a weak follow up to Piano Man called Streetlife Serenade), Joel has reassured his fans and impressed upon new listeners that his tremendous talent will leave a lasting impression on the pop musical world.

ALTHOUGH The Stranger has ended his absence form the airwaves, it has not succeeded in getting the listening audience to accept Joel's diverse talent. To most, Billy Joel is still a stranger: they know him only as the piano man. But Billy Joel is much more than that, and The Stranger demonstrates his range of abilities. The experimentation of side two is still a bit rough, but Joel should not abandon his experiments. Along with the attempts at diverse types of music, Joel might do well to return with some instrumentals like "Root Beer Rag" and "The Mexican Connection," the two best cuts from Streetlife Serenade.

The musician who appears on stage in a gray business suit with a conservative tie and white Pumas has a wealth of talent. An innovative album like The Stranger is a welcomed addition to Billy Joel's music.