New Age He Is--but a Lightweight He’s Not : Music: Trumpeter Mark Isham, best known for his film scores, explores pop and progressive with integrity.

Trumpeter Mark Isham has been so busy scoring films and writing for other projects, he finds it hard to keep up his chops. That’s why he could be heard one night last December at the tiny Room Upstairs above Le Cafe in Sherman Oaks, not far from his home, playing a rare acoustic set with his regular band.

“It gives me an outlet to keep playing the trumpet, to keep up my technique,” Isham explained earlier this week by phone from his home in the Benedict Canyon area of Beverly Hills. “The trumpet is one of those instruments that if you put it down for very long, you lose it, and it’s real hard to pick up again. So I have to continue to find ways to keep playing. And there’s nothing better than having to go to a gig to force you to keep practicing.”

Isham, who won a Grammy earlier this year in the Best New Age Performance category, will put his technique on display tonight with his electric band (bassist Doug Lunn, keyboardist David Goldblatt, drummer Kurt Wortman) at the Coach House in San Juan Capistrano, and Sunday at the Strand in Redondo Beach. He says that he goes in and out of being bugged by his inclusion in the New Age category.

“I guess the only time it really bothers me is when somebody feels the term is a derogatory slur upon the quality of the music, just assuming that my music is lightweight and innocuous,” he says. “But times have changed. Peter Gabriel won in that category the year before, and it’s not too bad of a group to be part of.”

Pigeonholing Isham isn’t all that easy. He’s recorded with new-music mavens, including guitarist David Torn, and as part of the ensemble Group ’87 with Terry Bozzio, Patrick Hearn and Peter Maunu. Adventurous jazz keyboardist Art Lande has utilized his trumpet and producing skills, and Isham also can be heard on a handful of Van Morrison’s albums, including “Inarticulate Speech of the Heart” and “Live at the Grand Opera House Belfast.”

But Isham is probably best known for his work as a film composer, especially for his collaborations with director Alan Rudolph. Getting together with Rudolph, Isham says, “was one of those wonderful synchronistic things. (Rudolph had) just lost his composer on the movie ‘Trouble in Mind’ and had a copy of ‘Vapor Drawings,’ ” David Torn’s 1983 album that featured Isham. “He asked his producer to find out if I scored pictures. During that same time, I’d just finished my third picture and my agent said, ‘You’re at the next stage of your career. You’ve got some credibility. Why don’t you go out and see a lot of movies, get familiar with who’s directing, then tell me who you want to work with?’

“So that weekend I went out and saw a bunch of movies, one of which was (Rudolph’s) ‘Choose Me.’ I thought, ‘This guy is fabulous. I’d love to meet him.’ We were both looking for each other. When we found that out, a deal was quickly made.”

In addition to “Trouble in Mind,” which featured Marianne Faithfull singing the title song, the trumpeter also scored Rudolph’s “The Moderns,” which won a Los Angeles Film Critics Award for best score.

Isham, who has a 2-month-old son, has also written music to illustrate children’s stories, such as “The Emperor’s New Clothes” and “The Steadfast Tin Soldier” (recently released under the title “Songs My Children Taught Me”).

“I find when I work on these projects that I allow a certain sort of simplicity and directness, almost a naivete, to enter into the music--something I don’t think I would do if I were making a record for myself or for most film scores,” he says. “There’s something about these children’s stories that work on a very basic level--they’re so simple yet really elegant at the same time. And the music somehow has to match that.”

Having just returned from three weeks touring the East Coast, Isham and his band will finish the West Coast portion of their tour in Vancouver, Canada, at the end of the month. The busy composer has completed his score for “Little Man Tate” (which stars and is directed by Jodie Foster) and hopes to have a new album of his own in stores by early 1992.

While his recent Grammy winner sought to bridge the worlds of pop and progressive music with vocals from Irish singer Tanita Tikaram and a quirky arrangement of Rodgers and Hart’s “Blue Moon,” he doesn’t see himself moving much closer to a commercial sound.

“I’m not about to turn out some cloned dance track. But I also think real pop music can have a certain amount of life and freshness to it. At this point, it’s a very great challenge to work with that problem: How do you keep a music’s integrity completely intact and expand your audience at the same time? That’s perhaps more of a challenge than writing the next great avant-garde stuff of the future. I’d like to do both.”

M ark Isham plays tonight at 9 at the Coach House, 33157 Camino Capistrano, San Juan Capistrano. Tickets: $17.50. Information (714) 496-8927. Also Sunday at 7:30 p.m. at the Strand, 1700 S. Pacific Coast Highway, Redondo Beach. Information: (213) 316-1700.