THE EDITOR of a Spanish record magazine, preparing a special issue in honor of the centenary of sound recording, has asked a number of critics in various countries to select a single recording each as the most important one produced in this first hundred years. It is an impossible task, of course - choosing the best 100 would be frustrating enough - but Gilbert Kalish's newest package of Haydn sonatas for Nonesuch (his third disc in what may eventually become a complete cycle) would be a reasonable nominee among all the piano recordings produced to date.

When all the factors are considered, this notion does not seem as hyperbolical as it must at first. There is greater music for the piano, to be sure, and such titans as Hofmann, Rubinstein, Horowitz, Schnabel et al. have committed some extraordinary performances to discs; but Kalish, in this particular repertory, is not out of place in such august company, and none of these others ever had the advantage of such glorious sound in any of their recordings. If we consider, then, the quality of the music itself, of the performance, and of the reproduction, this ecomomical disc must be acknowledged as not only a genuine bargain, but the realization of an exalted ideal.

In his recordings of Ives, Schoenberg, Crumb and other moderns, with the Contemporary Chamber Ensemble and other new music specialists, Kalish earned a reputation as an expert in the music of our own century, but that is only the tip of an iceberg that goes very deep. In the first of his Haydn discs, issued about two years ago, he showed a remarkable identification with the sonatas, suggesting both lifelong intimacy with the material and a sense of delighted discovery the listener can hardly fail to share. The second installment, issued last year, upheld that impression, and Vol. III (Nonesuch H-71344) now surpasses them both - in its finesse and interpretive profundity, if not entirely in its musical content.

The four works presented are the Sonatas Nos. 28 in E flat, 36 in C-sharp minor, 41 in B-flat and 49 in E flat, according to the Hoboken listings - Nos. 43, 49, 55 and 59, respectively, in the Vienna Urtext Edition of the late Christa Landon (a victim of that recent Portuguese airliner crash), which Kalish uses in his performances. These are not among the most frequently heard of Haydn's sonatas, but that only means the feeling of discovery is a little sharper and more delightful, for every one of them is a gem, and it is impossible to imagine performances yielding more of their essence than Kalish's. He sounds as if he has lived with them all his life, all the while deepending his respect, affection and understanding.

The sound of his Baldwin SD-10 (which must be the most grateful of pianos for purposes of recording) has been captured with exceptional realism by the engineering/producing team of Marc Aubort and Joanna Nickrenz, and what they taped has been transferred to disc with almost incredible fidelity by Robert Ludwig (whose very name by now is the most reliable assurance of exeptional mastering). The final icing on this scrumptious aural cake is that there is no icing at all: the surfaces are the most silent Nonesuch has yet achieved. Annotation by H.C. Robbins Landon, of course: nothing less would do for so outstanding a Haydn release.

Another Haydn series that is continuing with distinction is Philip's recording of the complete piano trios (this time in the critical edition of Robins Landon himself) by the Beaux Arts Trio. The latest installment, Vol. IX (Philips 9500 326), offers the earliest material yet presented in the series - Hoboken Nos. 7 in D, 9 in A and 12 in E minor (Landon Nos. 20, 22 and 25).All three are likely to be new to most listeners; they are from the period 1782-1788, during which Haydn composed such masterworks in other forms as his opera Orlando Paladino and the Oxford symphony, and they are hardly less meaty.

The performances, as on the eight preceding discs, are about all one might ask, and the sound has the realism and warmth of the sort of room for which the trios were designed. The side layout, however, continues to be a source of exasperation: as on all but one of the earlier releases in the series, there are three works of approximately equal length, on oe of them sandwiched between the other two in such a way that it is interrupted for turnover between movements. In this case, the timings indicate this could have been avoided: the D major and A major trios would have fit on a single side without undue crowding; in most cases, indeed, Philips could give us four trios to a disc instead of three, and in every case might exercise enough thoughtfulness to avoid violating the basic premise of the long-playing disc. But . . . this is the way Philips has done it up to now, and, despite this gratuitious irritation, the series is too good to miss.