Sonic surprises from the Lovely Music troupe

If you have a taste for both music and adventure, you should know about Lovely Music, a record company where anything can happen. Its catalog ranges from electronics to rock, from ''Western Classics'' to ''Rhythms for Computer and Percussion.'' What ties it all together is a refusal to be predictable, and a cheerful disregard for traditional boundary lines.

In celebration of itself, Lovely Music is presenting a month-long festival of ''Music for a New Year'' at Marymount Manhattan Theater here. Running through Jan. 30, it features live performances by such Lovely artists as electronic composer Alvin Lucier, pianist David Tudor, drummer David van Tieghem - who doesn't limit his playing to musical instruments - and a number of neorockers including Peter Gordon, Rhys Chatham, and ''Blue'' Gene Tyranny.

For fans of Lovely Music, it's an opportunity to examine firsthand some of the liveliest explorations on the current scene. For others, it's a sampler of recent Lovely activity, which remains available on disc to anyone hankering for sonic surprises. As it proceeds, the festival will undoubtedly offer clinkers as well as thrills. But chances are it will be innovative to the end.

Certainly it began that way, with an eccentric new opera by Robert Ashley, a leading video artist and experimental composer, who used to head the respected Once Group. Just back from a European tour, Ashley was on hand to star in ''Atalanta (Acts of God),'' which is slated to play Detroit in March, Philadelphia in April, and other cities after that. Its performances in the Lovely series marked its American premiere.

The setting is a bank, visible on a large TV screen at the left side of the stage. Near it stands Ashley, chanting stream-of-consciousness monologues into a microphone. Behind him sit two other performers, also chattering, while ''Blue'' Gene Tyranny doodles on a couple of keyboards and a second musician does something or other behind a low wall at the rear. This goes on for three acts, divided by spoken ''anecdotes'' with the curtain down.

What does it all mean? Quite a lot. First, it exemplifies Ashley's fascination with music as a group event, using materials ''composed'' in advance but developed on stage with a jazzlike spontaneity. It's not improvisation, Ashley said during a backstage conversation, because ''that implies a kind of architecture which you build on.'' Rather, he goes for ''spontaneous invention, '' free of predetermined ideas. ''Every three minutes we invent a new sound,'' he remarked.

Second, the opera meshes verbal and visual imagery with this musical format, to create a seamless (though rather colorless) multimedia experience. It doesn't have the excitement of some Ashley video work. But an elegant sense of structure flows from its careful combination of elements - freewheeling sound, austere decor, and conservatively composed TV images falling in between.

Third, the work illustrates Ashley's unconventional notions of language. Like director Robert Wilson, he considers sound more important than content when using speech on stage. So he reverses the priorities that usually apply to talking. ''You first establish the sound of the piece, as a composer, and give it a chance to generate ideas,'' he says. ''The content comes from the sound.'' Speech is a major artistic ingredient in ''Atalanta,'' as in most of the records Ashley has released on the Lovely label. Though music seems to be his main concern, ''you can't get words out of guitars,'' he says.

''Atalanta'' is the first part of an Ashley trilogy. The other sections are ''Perfect Lives,'' which he hopes will be broadcast on television later this year, and ''Now Eleanor's Idea,'' which he is composing now. Respectively, the three works deal with ''architecture, agriculture, and genealogy.'' Strange new stuff - now fascinating, now monotonous, but provocative all the way.