WITH THE arrival of compact disc, the "fully digital" playback medium, we have been reminded that digital recordings on conventional analog LPs were reaching us in only a "semi-digital" state. With the record companies remastering some of their choice analog recordings digitally in order to transfer them to compact discs we're getting a different sort of "semi-digital" product, and now RCA is offering what might be called "hemi-demi-digital" LPs in its low-priced Gold Seal reissue series.

In the last few years RCA has done some remarkable revitalizing of early stereo recordings through half-speed remastering. These stunning reissues of famous performances, taped in the middle and late 1950s by the Chicago Symphony Orchestra under Fritz Reiner and by the Boston Symphony under Charles Munch, were issued on "audiophile" pressings at the same price as new digital recordings. Now RCA has gone back to the same source, and to some recordings made as recently as eight or nine years ago by Ormandy, Stokowski, Fiedler and other conductors, and has remastered them digitally from the original master tapes. This series is not mastered at half-speed and does not get "audiophile" pressings, but it's pretty nice at a list price of $5.98.

RCA is being discreet about it--not printing "DIGITAL" in big letters on the jackets, and not on the disc labels at all. All that does appear to identify these special reissues is the notice, "Digitally remastered analog recordings," in modest-sized print in a corner of the record cover. The covers themselves all follow the same layout--a stylized postage stamp bearing a picture of the respective performer, against a postal cancellation background--and carry the heading "Legendary Performers" (apparently a response to the CBS "Great Performances" series). All are available on cassettes as well as discs.

Many of the 20 items in the series so far were "sonic showpieces" in their time, and several of the performances are indeed "legendary." The improvements discernible now are a greater degree of clarity and definition throughout the aural spectrum, a modest opening up of the dynamic range and a total absence of background hiss or other noise.

At the top of the list, I would cite two items with Reiner and the Chicagoans: their incomparable version of the Bartok Concerto for Orchestra, recorded in 1954 (AGL1-5220; cassette AGK1-5220), and the brilliant collection of Rossini overtures taped four or five years later (AGL1-5210; cassette AGK-5210).

Among other good bets: Henryk Szeryng in the Brahms Violin Concerto with Pierre Monteux and the London Symphony Orchestra (AGL1- or AGK-5216); Itzhak Perlman's first recording of Lalo's "Symphony espagnole," with Andre' Previn and the London Symphony (together with Ravel's "Tzigane," AGL1- or AGK1-5208); Stokowski's last recording of Rimsky-Korsakov's "Scheherazade," with the Royal Philharmonic (AGL1- or AGK1-5213); Ormandy's last Shostakovich Fifth, not as searingly intense as the new Rostropovich, but a handsome account in its own right (AGL1- or AGK1-5214); Ormandy again in "The Planets," by Holst (AGL1- or AGK1-5207); Ormandy yet again in the Mussorgsky/Ravel "Pictures at an Exhbition" and Ravel's "Bole'ro" (AGL1- or AGK1-5209); Munch and the Boston in Tchaikovsky's Serenade for String Orchestra and "Romeo and Juliet" (AGL1- or AGK1-5218).

Now that these recordings have been remastered digitally, they could, of course, be transferred to compact discs, and RCA advises that a low-priced, compact disc line is possible if it becomes economically feasible. (The rejection rate in compact disc production was as high as 90 percent initially, and is still 50 to 60 percent, a factor that will keep costs high for some time.) For now, it will be interesting to see which reissues RCA assigns to this series and which to the "Point 5" half-speed-remastered series--and whether these twain shall ever meet.