Stevie Wonder's "Journey Through the Secret Life of Plants" (Tamla T13-371C2) will test the adaptability of his fans. Of the 20 cuts on the two-record set, only nine are fully developed songs. Three others are mere song fragments, while the other eight are instrumentals. As the liner notes put it, "substantial portions of the album" are from the soundtrack of the yet unreleased movie, "The Secret Life of Plants."

Much of the music removes Wonder further than ever from his roots in Motown soul music. There's a sitar instrumental, a church requiem, an African percussion jam, a bebop jazz trio piece, a Japanese chorale, gorgeous pop melodies and lots of experimental synthesizer.

Some of Wonder's experiments fail. Some of the instrumentals lapse into the sentimentality and cuteness of movie soundtracks. Two songs and one fragment use the dubious tactic of feeding Wonder's vocals through synthesizer distortion so he can portray plants or insects. Silly.

But there are plenty of successes and a few breakthroughs. Edited down to one record, the album could have been a classic. Even stretched out over two discs, the high points rank with the year's best.

As always, Wonder's saving grace is his command of melody and harmony. On his most radical synthesizer instrumentals, a melody emerges from the buzzing, soaring electricity.

The album opens with an immediate test for the faithful: 13 minutes of three instrumentals -- "Earth's Creation," "The First Garden" and "Voyage to India." As the titles imply, these pieces resemble Stravinsky's "Rite of Spring" as it was used in Disney's "Fantasia."

"Earth's Creation" unfolds as a synthesizer sounding like echoing thunder sets an epic rhythm. Then a second synthesizer sound emerges like a high-pitched swarm of primeval insects. Finally a third synthesizer sound ebbs and flows like a forming sea.

The fourth cut, "The Same Old Story," is the first song and much more familiar territory. A typically lovely Wonder melody is set to an easygoing tempo. Ben Bridges and Michael Sembello pick folksy acoustic guitars while Wonder plucks an acoustic bass and warbles his harmonica. The instruments produce a bubbling, popping sound.

Wonder's lyrics have always been his biggest weakness, and they are again here. He sounds like those snappy biology texts that toss around words like "ecology" and "biosphere" with more flair than clarity. Wonder oversimplifies pollution ("Man's production/Life corruption/World destruct"), ecology ("what we see as insignificant/Provides the purest air we breathe") and love ("I know people say two hearts beating as one is unreal").

Wonder does make musical breakthroughs, however -- and the most important is his taming of the synthesizer. Since their arrival in pop music some 13 years ago, synthesizers have ruined far more records than they've enhanced. They produce a dazzling array of sounds, but have remained stubbornly impersonal.

Only Joe Zawinul, Chick Corea, Brian Wilson, Garth Hudson, Bernie Worrell and Wonder have managed much nuance with synthesizers, and no one has accomplished what Wonder does. Never have synthesizers sounded so voice-like, so able to stretch and bend notes for inflections.

As he has on all his recent albums, Wonder plays almost all the instruments himself. On "Journey Through the Secret Life of Plants," he plays all the instruments on 11 cuts and all but the guitars or sitar on five others. On all but a few instruments, Wonder justified his do-it-yourself approach. He certainly has few peers on synthesized or regular keyboards.

This year he shows off newly acquired skills on the acoustic bass. And while almost everyone else uses the harmonica for full bluesy chords, Wonder uses it for single-note lyricism, making it sound almost like a Dixieland clarinet. His drumming still leaves a lot to be desired.

It's significant that the only cut on the album with real propulsion is the only one Wonder recorded using a band. The medley of "A Seed's a Star" and "Tree," apparently recorded live in Africa, is powered by the driving beat and crackling energy of the eight-man band. With his hand, Wonder loses in clarity and nuance, but gains in power and rhythm. This success makes one wish there were more band efforts on the new record.

The vocal version of "Send One Your Love" deserves its selection as the album's first single. Wonder sends ascending melodic lines through two or three different chord progressions. Each ascent squeezes out new pleasure. Keys and themes shift repeatedly; bass notes slide and bend; synthesizer notes seem to sprinkle from above; the harmonica breaks almost seem to whistle.

This and three other songs are firmly in the style that made Wonder popular, and may carry listeners past the movie muzak and along with his adventures into new musical fields. After a three-year wait since his last album, Wonder has reemerged with his melodic gift and creative restlessness intact.