The latest entry in the compact disc price wars is a flock of butterflies -- 20 of them, ranging from the darkly glowing red-and-gray Pierella incandescens to the flamboyant brown, cream and orange Adelpha erotia. Under their collective French name, "Papillon," these and 18 other exotic creatures decorate the first issues in a new midprice series of compact discs from RCA.

That noise you may have been hearing in the background is the sound of CD prices falling and smashing. The arrival of RCA's "Papillon" discs consolidates this trend, which is probably the year's most important development in classical record marketing.

Drawing on RCA's magnificent archives, the new series also sets dazzling performance standards in the field of midprice CDs. The material is basic classical repertoire, the performers are among the world's best and best known, and each disc contains more than an hour of music, with times ranging from 63:11 for Ozawa's "Carmina Burana" to more than over 71 minutes for discs of Richter, Perlman and Ormandy.

Each item in the series has its own butterfly, prominently displayed and identified with its Latin name. The butterflies not only give the series a striking visual identification for collectors; they also symbolize neatly what has happened to the music inside the package. Like the creature that begins as a caterpillar and becomes a butterfly, the music on these discs was recorded originally on analog equipment, except for Uto Ughi's digitally recorded Mendelssohn Violin Concerto. Now, the material has been metamorphosed, butterfly-like, into bright, clean digital sound.

On the whole, the image is valid. The recording dates for this material range from 1951 (Monteux's "The Rite of Spring") to the 1980s. The center of gravity is the early 1960s for such conductors as Fiedler, Reiner and Leinsdorf, the '70s for Ormandy. Some of the discs have a discreet warning in the notes that those with wide-range equipment may notice occasional traces of tape hiss. But for the average listener, with ordinary playback equipment and ears somewhat less acute than Fido's, this is not likely to be a serious problem. In general, these familiar recordings now sound better than they have in any previous commercial packaging.

All 20 items in the first Papillon release offer excellent value, though naturally, selection among them will depend largely on personal taste. My first choice, over serious competition, would be Itzhak Perlman's brilliant interpretations of the Lalo "Symphonie Espagnole," the Sibelius Violin Concerto and Ravel's "Tzigane" (6520-2-RG). Other top choices (roughly in order of preference) would include Julian Bream playing guitar concertos of Rodrigo and Villa-Lobos (6525-2-RG), Lynn Harrell and James Levine collaborating in Dvorak's Cello Concerto and Schubert's "Arpeggione" Sonata (6531-2-RG), Fritz Reiner's 1961 Beethoven Ninth from Chicago (6532-2-RG), Seiji Ozawa's version of Orff's "Carmina Burana" (6533-2-RG), and Fiedler's Gershwin (6519-2-RG), a generous selection with Earl Wild as the brilliant piano soloist, that includes "Rhapsody in Blue," Concerto in F, "I Got Rhythm" Variations and "An American in Paris."

In a set of discs that has no real weaknesses, these seem to be the strongest in material, performance and sound. But many tastes might prefer the Verdi arias and duets sung by Placido Domingo and Katia Ricciarelli (6534-2-RG, with texts and translations), or Uto Ughi's persuasive performance of the Beethoven and Mendelssohn violin concertos on a single disc (6536-2-RG), or James Galway's performance of four Bach works with the Zagreb soloists (6517-2-RG), recorded at a time when he was less affluent and less glib than today.

Boys choirs are not everybody's cup of tea, but those who like this very special kind of sound will go wild for Papillon 6535-2-RG, which features the Vienna Choir Boys as choral and solo trebles, with Hans Gillesberger also conducting some of Vienna's best adult musicians, in Mozart's Requiem and "Ave Verum Corpus" and Haydn's "Te Deum." These are totally idiomatic and very musical interpretations.

For many, the highlight of the first Papillon release will be Stravinsky's "The Rite of Spring" and "Petrouchka," with Pierre Monteux conducting the Boston Symphony Orchestra (6529-2-RG). The sound is not equal to the best current digital recording, and in "The Rite of Spring" it is not even stereo, but these facts are offset by the authority of Monteux's interpretation -- he conducted the world premieres of both works -- and by the quality of the 1950s-vintage Boston Symphony, a great orchestra in its prime. There are several other discs (considered the ultimate in sound technology 25 or 30 years ago) in which dazzling content triumphs over relatively "primitive" recording techniques: a Tchaikovsky double feature with Misha Dichter playing the Piano Concerto No. 1 and Perlman playing the Violin Concerto (6526-2-RG), a Rachmaninoff double feature with Vladimir Ashkenazy playing the Piano Concerto No. 3 and Leonard Pennario playing the Paganini Rhapsody (6524-2-RG), Charles Munch conducting the Boston Symphony in five Ravel compositions (6522-2-RG), and Sviatoslav Richter's brilliant and sensitive performances of the Brahms Piano Concerto No. 2 and Beethoven's "Appassionata" Sonata (6518-2-RG).

In competition with Papillon, MCA Classics, another excellent line of midprice CDs, offers performers with less name recognition (at least in the United States) but performances that are invariably solid and reliable. MCA's chief advantage over RCA and most other midprice lines from the big companies is that all of its recordings are recent and completely digital. If you have speakers that cost more than $10,000 and ears to match, you may want this thoroughly modern recording technology in your collection, with performances that can be trusted. They can also be trusted on bargain loudspeakers, but good sound is a strong selling point for this line.

Earlier in the year, when it was being launched, MCA Classics stuck resolutely to the classical Top 40, but it is now becoming a bit more adventurous. Its latest release includes a collection of "Great Coloratura Solos" dating from the 18th to the 20th century, featuring soprano Beverly Hoch, with Kenneth Schermerhorn conducting the Hong Kong Philharmonic (MCAD-25966). Particularly noteworthy and excellently sung are Milhaud's "Chansons de Ronsard" and Glie`re's Concerto for soprano and orchestra. Most of the 19 Latin American selections played by Marcelo Kayath on "Latin Guitar" (MCAD-25963) will be unfamiliar, except for the elemental Five Preludes of Villa-Lobos. But they are enchanting and well played. On "Impressions of France" (MCAD-25969), pianist Cristina Ortiz idiomatically interprets unfamiliar works of Chabrier, Faure', Ibert, Poulenc and Milhaud along with more familiar works of Debussy, Ravel and Satie.

The prime attraction of "A Little Night Music" (MCAD-25162) could hardly be more familiar: Mozart's "Eine Kleine Nachtmusik" exquisitely played by the conductorless Serenata of London. But the record is filled out with three other works that deserve to be better known: Mozart's "Serenata Notturna," Elgar's Serenade for Strings and Grieg's "Holberg" Suite" -- a program as beautifully chosen as it is beautifully played and recorded.

Still, the backbone of this new midprice line is (as it has to be) the basic classical repertoire. In its latest release, some of the best items in this category include "The Vienna of Johann Strauss" (MCAD-25967), Barry Tuckwell conducting the London Symphony in six Wagner overtures (MCAD-25968), Stanislaw Skrowaczewski conducting the Halle' Orchestra in the Second Symphony and Tragic Overture of Brahms (MCAD-25160), and excellent performances of Mozart's Clarinet Concerto and his Concerto for flute and harp (MCAD-25965).

MCA Classics lacks the historic background of RCA as a classical recording label, but it has been buying some recorded archives -- notably those of the defunct American Decca label, which are now being sifted for reissues. These archives include some classic performances by countertenor Russell Oberlin, harpsichordist Sylvia Marlowe, the New York Pro Musica and other American artists of the '50s and '60s. But their heart and soul are the recordings of the late Andres Segovia.

The first two volumes of the "Segovia Collection" have just appeared on MCA compact discs, and they are a model of how such material should be recycled. The selections are grouped thematically, each of the discs contains more than an hour of music, and the sound has been scrupulously transferred to the new medium from the best sources available. The first volume (MCAD-42068) is dedicated to Segovia playing his own Bach transcriptions: music originally composed for lute or unaccompanied violin or cello. Volume 2 (MCAD-42067) features three of the countless pieces composed for and dedicated to Segovia: Rodrigo's "Concierto de Aranjuez," Ponce's "Concierto del Sur" and Torroba's "Castles of Spain."

In some of the best material of Vol. 1 -- the "Gavotte en Rondeau" from Violin Partita No. 3, for example, or the monumental Chaconne from Partita No. 2 -- the recording predates the stereo era. But that matters little for a solo guitar; the sound is finely detailed (including an occasional nail scraping on a string), and the instrument has a vivid presence.

Even more important, for those who witnessed Segovia's diminished powers in his last few concert tours, these recordings present him in his prime, a quarter century ago or more, but with the impact of digital sound. These records should be in the collection of anyone who is deeply interested in the classical guitar