It came to him in a dream.

Rhythm-and-blues musician Merl Saunders had never been to the rain forests of South America. He'd read about them. He'd seen pictures of the beauty and the destruction. But he hadn't visited them -- until he had this dream.

"When I woke up, I said, 'I've got to do a number about this.' "

So he wrote "Blues From the Rainforest," a 15-minute-long suite of synthesizers, percussion by the master Maruga and sounds of the forests -- birds, crickets, all sorts of endangered animals. For a final touch he invited his longtime pal and fellow San Franciscan, legendary Grateful Dead guitarist Jerry Garcia, to add a few notes.

It was recorded in one take.

"About three years ago, if you told me I was going to do an album on synthesizer, I would have laughed at you. I play organ and goof around with synthesizers, but it's like a little toy. Then the sounds started to develop, and the rain forest album came out if it."

The song was premiered at the Earth Day Concert last April in San Francisco.

"It was kind of overcast, and the people weren't really paying attention," he recalls. "I came out and said, 'If the trees could talk, this is what they'd say.' I struck the first note and it started raining. It was about the highest high I've ever had."

Saunders has been involved with environmental issues for a long time. In 1971 he recorded "Save Mother Earth," a tune, he says, that "was big on the college campuses."

"My philosophy," he adds, "is that we must preserve the world so we can still boogie."

Once he recorded "Blues From the Rainforest," he had another dream. It was about a Hawaiian sunrise. It metamorphosed into "Sunrise Over Haleakala," a synthesizer and guitar duo, also featuring Garcia.

Saunders hadn't been to Haleakala when he composed the piece. But he went there two weeks ago. "It's a crater with an elevation of close to 19,000 feet. And I saw the sunrise. The music fits. It was quite emotional.

"And at the time I wrote the song, I didn't know there was a rain forest there behind it that they are destroying."

All the songs on "Blues From the Rainforest" (Summertone Records) came from dreams, except one -- "Afro Pearl Blue."

"I did the music like an out-of-body experience," says Saunders. "I have had one, and so has Maruga. Jerry had an out-of-body experience laying on the floor before a {Grateful Dead} show too. And I said, 'Jerry, play that out-of-body experience -- just how you felt it.' "

Merl Saunders is performing at the Bayou on Thursday night at 9. Tickets are $10.50 and available at Ticketron. For information, call (202) 333-2897.