The sound could have been wretched. The title performance could have been a loss. The orchestra could have been ragged and the chorus out of tune. All those things notwithstanding the new version on Angel of Mussorgsky's "Boris Godunov" would be a landmark recording.

That is because he did not write "Boris" in the form in which the world has come to know it. This searing musical portrait of an actual Russian ruler who murdered his way to the top and then was consumed with guilt is commonly performed in a dressed-up, cleansed and inflated rearrangement of "Boris" done by Rimsky-Korsakov after its composer's death.

Only in the last few years has what Mussorgsky actually wrote attracted the attention of musicians, and only with Angel's new version has it been recorded. The Boris is the bass Martti Talvela, who will open the season at the Metropolitan Opera Monday night in this version. His performance, and the recording in general, may not be definitive, but it is quite splendid.

To the ear, the restored "Boris" is often distinctly different from what Rimsky wrought. The stark, brooding character of the work, and of the central figure, in particular, as sharper. The work seems all the stronger.

Rimsky thought he was doing his deceased friend a favor by polishing up an opera that he thought unstageable because of its musical crudities. So he reorchestrated, made extensive cuts, changed some of the more jarring notes and added new material that would make "Boris" seem easier on the 19th-century ear. But what seemed crude then was merely prophetic of where music was headed.

Obviously "Boris" is still a master-piece Rimsky's way, but the emphasis is more on splendor than on pathos. And with Rimsky's flamboyance stripped away, Mossorgsky's dramatic vision seems all the more true.

This poses a unique complication for the buyer who wants only one "Boris." Though the new Angel cast is generally excellent, it is up against tough recorded competition from earlier versions. Talvela's Boris is almost lyrical, in a role where the tradition, as derived from the famous Chaliapin characterization, has been to perform melodramatically. On stage Talvela is particularly effective, because he has the large physique one expects of such a czar. But if you feel the need for commanding sonority in a Boris. Talvela does not match such distinguished recorded predecessors as Christoff, London, or (in excerpt form) Chaliapin or Pinza.

Nicolai Gedda is predictably suberb as the false Dmitri, bot not better than he is in the part on both Christoff versions. The overall level of the others is orchestra and chorus are very good (under Jerzy Semkow), but they have the problem of being up against their awesome Bolshoi counterparts on George London's version.

All said, though, hearing this recording is a genuinely exciting experience - and not just because it's at last giving us the original version. Anyone with a special fondness for "Boris" should buy it.