The piano is the easiest and most difficult of musical instruments. Easy because anyone can play it immediately -- at least a little bit. You push a key and out pops a note. In contrast, a beginner on the violin, flute or oboe can work for months before producing a note that doesn't bring tears to a listener's eyes.

But it may take a pianist years of practice to make the instrument sing like a violin, flute or oboe in the hands of a master performer. The piano's advantage is also its problem: it is essentially a machine activated by levers, not by the human breath or the direct touch of a hand on a vibrating string. The pianist can produce cascades of notes comparable to a whole orchestra of string players, and his instrument can roar with a power beyond dozens of flutes. But delicacy, intimacy, the special emotional communication that happens when the instrument reminds you of a human voice -- that is something for which the pianist must put in long hours of hard work.

An object lesson in how it can be done is supplied by Abbey Simon on a CD (Vox VU 9004) of piano music inspired by violin music: the six Paganini Etudes of Franz Liszt and the monumental Variations on a Theme of Paganini, Op. 35, by Brahms. This music demands virtuoso technique, and Simon has plenty, but he makes his strongest impression by the flexibility and expressiveness of his phrasing, the subtle gradations of his dynamics.

I like Simon's performance of the Paganini variations better than the excellent one by Gerhard Oppitz in his set of Brahms's Complete Piano Works (Eurodisc 69245-2-RG, five CDs available separately), but that is largely a matter of personal taste. Nobody could be equally at home in the three sonatas and scherzo of Brahms's youth, the five sets of variations, the ballades, rhapsodies, romances, waltzes, caprices, fantasies and intermezzi scattered through his career, but Oppitz is technically solid and always interesting. Those who prefer to get a complete set rather than mix and match the work of various pianists will not be disappointed by Oppitz.

The "Goyescas" of Enrique Granados are subtly descriptive piano pieces, inspired by the romantic paintings of Goya, which the composer later reworked into a short, atmospheric opera. The piano version, intensely evocative of a bygone Spain, is probably the composer's masterpiece. Alicia de Larrocha has been so busy in recent years with the music of Mozart, Beethoven and Chopin that one might forget her special affinity for Spanish piano music, but on RCA 60408-2-RC, she plays the "Goyescas," plus a few other works of Granados, with a totally idiomatic style and electrifying technique.

The hottest pianist on the scene right now is Evgeny Kissin, who will be 20 in October and who began his career in the Soviet Union when he was 10. He has been praised in this column several times for his remarkable recordings on the RCA label, but he made his first strong impact in this country Sept. 30 in his Carnegie Hall debut. That event is now available from RCA on two CDs (60443-2-RC) that make it clear why the New York audience got so excited. Kissin is a very accomplished young player, adept in the instrument's whole repertoire, though he has a special affinity for the Russians -- Prokofiev, Shostakovich, Rachmaninoff and Scriabin. He is phenomenally strong, fast and accurate, as we expect young players to be, but he can also make the piano sing. For most listeners, the highlight of the set will be Prokofiev's Sonata No. 6, which is played brilliantly, but I am also impressed by several Liszt pieces (notably the "Rhapsodie espagnole"), a sensitively played Chopin waltz and Schumann's "Abegg" Variations, Op. 1 and Symphonic Etudes, Op. 13.

Sony Classic has nicely timed its release of a 1987 Kissin recital in Tokyo (SK 45931) to catch this surge of interest. On this disc, too, the main attraction is unfortunately Prokofiev's Sixth. Perhaps this is not unfortunate for those who would like to compare versions and see how Kissin has changed in a bit less than four years. He has matured some, but he was phenomenal in 1987 and this music is not the best for displaying the mellow ripeness of his advanced years. The Sony disc is treasurable, in any case, for some beautifully executed miniatures -- notably Rachmaninoff's "Lilacs," with which it opens, and pieces by Liszt, Chopin and Scriabin.

One of the most charming piano records I have heard in a long time is played by Ruth Laredo and titled "My First Recital" (ESS.A.Y CD1006). The cover shows her, at 10, playing in public; the contents are what you might expect at the debut recital of a very talented young pianist, but played with the finesse of the mature, world-class artist Laredo has become: Beethoven's "Fur Elise," of course, but also his Sonata in G, Op. 49, No. 2; Mozart's familiar little Sonata in C, K. 545, and his Fantasia in D minor, K. 397; a prelude from the "Well-Tempered Clavier" and three of Bach's Two-Part Inventions; a few Chopin waltzes, some Debussy (including "Clair de Lune," naturally) and a bit of Schumann (including "Traumerei," of course). The performances may inspire young pianists to work harder and will certainly show them what to shoot for, but they are intensely enjoyable for listeners (such as yours truly) who have no hope of ever playing the piano like that.

Two piano records from Connoisseur Society offer quite good performances of Bach's "Goldberg" Variations and Chromatic Fantasy by Samuel Bartos (CD4176) and music of Scarlatti, Beethoven and Brahms by Mordecai Shehori (CD4177), but the primary attraction is the extraordinarily lifelike sound. The piano is a difficult instrument to record, but producer E. Alan Silver and his In Sync Laboratories make it sound easy. Shehori also plays Brahms's Paganini Variations, by the way, and plays them extremely well, but I still like Simon's subtle sonic lights and shadows best.

With his fourth volume in the series "Percy Grainger 'Dished up for Piano' " (Nimbus NI 5255) Martin Jones completes his survey of the complete piano music of this curious but unquestionably talented figure. This final CD is a miscellaneous collection of odds and ends: juvenilia, little pieces d'occasion, and transcriptions from other composers, including a familiar melody from Handel's "Water Music," a strange condensation of the first movement of Schumann's Piano Concerto and a very effective performing version of Bach's Toccata and Fugue in D minor largely plagiarized from other transcribers. Of interest mostly to hard-core Grainger fans, but well-played and annotated.

Piano transcription, which did for the 19th century essentially what recordings have done for the 20th -- make orchestral or operatic music available in the home -- has been largely neglected on records, but that situation seems to be changing. The two most notable transcribers in the history of the piano, Franz Liszt and Ferrucio Busoni, are well represented on new CDs from Dante, a small label that specializes in unusual piano repertoire.

Geoffrey Douglas Madge, who has made some extraordinary recordings of Leopold Godowsky's music, has begun a complete survey of Busoni's transcriptions from Bach. Volume 1 (PSG9011) has the complete organ chorales, the Toccata, Adagio and Fugue in C (BWV 564) and the "Ste. Anne" Prelude and Fugue, BWV 552) played with unspectacular precision and the kind of linear clarity one finds in a good baroque organ. In "Liszt Visits Vienna" (Dante PSG9012), Joseph Villa plays some of Liszt's transcriptions (or, more often, adaptations) from Beethoven ("Adelaide" and the "Ruins of Athens" Fantasy) and Schubert (March No. 2 in B Minor and "Soiree de Vienne" No. 7). Villa has a self-assured virtuosity that does not need to exaggerate to call attention to itself, and he integrates Liszt's brilliant inventions into cogent, coherent musical statements.

Most of Debussy's orchestral music also exist in a piano version -- usually the composer's original draft, sometimes a later reduction by Debussy or a colleague. Some of these are gathered in a collection by pianist Boaz Sharon titled "The Unknown Debussy" (Unicorn-Kanchana DKP9103) with moderate accuracy. The ballet "La Boite a Joujoux" ("The Toybox") and the Prelude to "L'Apres-midi d'un faune" ("The Afternoon of a Faun") are hardly unknown, though the piano versions are unfamiliar. On the other hand, the two little fragments from his unfinished incidental music to "King Lear" and the habanera mysteriously titled "Lindaraja" are likely to be unfamiliar, and all the music including the transcriptions from the decadent "Martyrdom of St. Sebastian" work well as piano music. Sharon presents its values eloquently.