LUCIANO BERIO did not necessarily conceive his ''Sequenzas'' to be heard together as a cycle. Virtuosic and intense works for solo instruments (including voice), they make for compelling though not easy listening. But they seem to be heading toward a kind of monumental memorialization, like that of Beethoven's piano sonatas or the preludes and fugues of Bach's ''Well-Tempered Clavier.''

Three years after Berio's death, two complete recordings of the ''Sequenzas'' -- 14 works (with variants), written over nearly five decades -- have come onto the market: one, on four CD's, from the independent label Mode; the other, on three CD's, from the budget label Naxos. They join a set that has been considered definitive, a recording by members of the Ensemble Intercontemporain, released by Deutsche Grammophon in 1999. But the new ones have at least one clear advantage: the final ''Sequenza,'' for cello, which Berio wrote only in 2002.

Disparate as they are, the ''Sequenzas'' have things in common. One is a kind of self-consciousness about the act of creating music in the specific language of a given instrument, often with reference to specifics of the instrument's history and performance. Many of the pieces proceed from a note or two, starting with defiant, repeated statements of a tone (like the Eighth, for violin) or winding their way around a sustained sound from without (like the 10th, for trumpet and piano resonance). Berio's concept of the term ''sequenza'' was that each piece would derive from a sequence of harmonic fields, a derivation that can clearly be heard.

Yet whether they assail (like the Sixth, for viola, which opens with a figurative grabbing of the listener's lapel) or lull (like the melodious Ninth, for clarinet), the pieces tend to follow a similar dramatic arc through spasms of activity back into quiet resignation. Berio wrings this drama from each instrument with a formidable range of technical means: special tonguings or bowings or beatings on the soundboard and, often, sounds that carry the performer to the brink of speech.

The Fifth, for trombone, which casts the player as a lugubrious clown, puts in his or her mouth a summarizing word, ''Why?'' This is a crowd of distinct voices, demanding attention, that taken together can wear on the senses. And since each piece rises and falls on individual performance, it is difficult to judge them as a group.

The Mode set, to be sure, offers a sense of having been officially sanctioned. The project took shape after performances at the 92nd Street Y of all the ''Sequenzas'' (then 13) for Berio's 70th birthday in 1995. Berio guided the choices of performers, and two of them (Stuart Dempster, the trombonist, and Rohan de Saram, the cellist) are the original dedicatees of the works for their instruments.

This set also aspires to be definitive, collecting every alternative version of each piece (the Sixth rearranged for cello, the Ninth for alto saxophone) as well as Berio's other works for solo instruments, like ''Gesti'' for recorder and ''Psy'' for double bass, which one might term ''Sequenzas Lite.'' An unexpectedly appealing feature is the inclusion of short spoken verses that the poet Edoardo Sanguineti, a collaborator of Berio's, wrote to accompany each ''Sequenza'': pithy and illuminating, they act like a sorbet to cleanse the palette between each rich course.

But the Naxos set has advantages even beyond its considerably lower price, like an elegant, even melting rendition of the clarinet sequenza by Joaquin Valdepe? The measure of a performer's success lies in the difference between merely executing the notes and internalizing them.

There is no single right approach. Mr. Dempster, not surprisingly, brings out a prodigious level of articulate nuance in ''his'' trombone ''Sequenza.'' Yet Alain Trudel, on Naxos, turns that ''Why'' into the statement of a frightened cartoon, which, at least momentarily, seems exactly what Berio intended.

Photo: Two labels recently released complete recordings of ''Sequenzas'' by Luciano Berio, left. The works for solo instruments make for compelling but not easy listening. (Photo by Philippe Gontier)