IT'S PROBABLY NOT FAIR to knock other people's marriages. Yoko Ono helped John Lennon to find himself. John is helping Yoko to find herself, too. But in finding themselves, either John or Yoko should have realized that Yoko can't sing. The double album Approximately Infinite Universe must set some record for discordant self-indulgence.

The problem's not so much the ideology behind Ono's songs. Her statement on "The Feminization of Society," which appears inside the record jacket, is an intelligent, if not too original or subtle statement of her political position. But she doesn't sing the statement. Therein lies the difference.

One wrote the lyrics and the music to all the songs in this package, and the music, at least, is intermittently promising. Ironically for an artist so insistent on the importance of an independent identity, her style at its best is strikingly similar to John Lennon's. Her band will come in with a bouncy drum and guitar introduction or a warm harmony of guitar and piano. Then inevitably she starts singing. It's really a shame.

There are problems, however, in the songs themselves. Some of her musical themes start out promising to be catchy or sad or rousing. Unfortunately, she doesn't expand on these motifs; no variations in rhythm or melody surround the original cores. The result is a group of songs--each with the rhythmic variety of a chain-link fence--which do, after a while, become a trifle wearing.

Her lyrics are instructive in an ironic way. They prove that good politics does not necessarily equal good music. What Ono hasn't learned is that an honest verbal expression of self does not constitute art unless the writer is honestly artistic. The words must capture a mood, an image, an idea with feeling to which others may grab hold to drift along with the song. How can you get excited about a lyric like:

People of America

When will we learn

It's now or never

There's no time to lose?

How can someone using a title as politically and emotionally suggestive as "I Have a Woman Inside My Soul" turn out verse as vapid as:

I have a woman inside my soul

Her eyes somber and sad

She waves her hand to try to reach me

But I can't hear what she says?

Of course, if a verse like this last one, without subtlety, originality or lyricism were sung with feeling to a stirring melody, who would notice the emptiness of the poetry? Paul and Linda almost got away with it for two albums. But Ono has trouble when she tries to carry a tune. Her voice tends to struggle, drop it, and break it.

Ordinarily, I wouldn't complain so much about music so trivial. Even her back-up band, Elephant's Memory, is approximately infinitely better than the material deserves. I wouldn't mind that Ono can't include even two enjoyable sides of music in a four-sided album. I wouldn't mind that she sings only stiff manifestos, enigmatic drivel, sentimental nonsense, or primal screams. What I do mind is a person who can use her connections to rip off the public and then pose as a liberator. Few other people could foist this embarrassment upon an audience, while far more talented people go unheard.