IN OCTOBER 1975 Antal Dorati conducted the National Symphony Orchestra in the first performances of his new Piano Concerto, with the solo part played by his wife, Ilse von Alpenheim, for whom the work was composed. Paul Hume wrote in his review that it "warmed the hearts of those who like their music romantic with unabashed sentiment."

The new Vox recording of the Concerto (Turnabout TV-S 34669), with the original personnel, was one of the last projects to squeak through the Ford Foundation's recently discontinued program of support to recordings of American works and, unless I am mistaken, the first commercial recording to be made in the Kennedy Center Concert Hall (Dorati's NSO recordings for London/Decca have been made in Constitution Hall). The production/engineering team has done a characteristically excellent job with the sound.

And that is only half of it - or a bit less than half. The nearly 32-minute Concerto is on a single side, with Alpenheim's masterly performance of another work her husband composed for her - the solo Variations on a Theme by Bartok (1971) - on side 2. The theme is the "Peasant Song," No. 15 of the Mikrokosmosmos of his own here, in 30 miniature variations and a finale that fit into a quarter-hour. He has also provided his own painting for the record jacket, and written the liner material on his wife and himself as well as on the two compositions. This is no ghost job: the unforced urbanity and charm of the man, as well as what might be called his joyous seriousness about music and music-making brighten every paragraph. The whole package is a thoroughgoing delight.

On the same label is a pair of Frank performances Dorati recorded with his English orchestra, the Royal Philharmonic: the Symphony in D minor and the Symphonic Variations, with Ilse von Alpenheim again the soloist in the latter work (TV-S 34663). These are among the few works in the standard repertory Dorati seems not to have recorded before, and both of them come off extremely well.

At the same time these two discs came from Turnabout, Philips released one on which Ilse von Alpenheim plays four solo works of Mendelssohn (9500 162). The Variations serisuses, Op. 54, composed in 1841, would seem to be the only one of the four that is otherwise available at present, outside of the Vox Boxes in which Rena Kyriakou plays all of Mendelssohn's piano music; it is also the only one of the four Mendelssohn composed after the age of 20.

The Sonata in B-flat, Op. 106, like most of Mendelssohn's works with opus numbers over 90, is actually a very early work that was published posthumously.He was only 18 when he composed the sonata in 1827, but already had the String Octet and the Midsummer Night's Dream Overture behind him. This Weber-influenced Sonata is a less consequential work than those, but a substantial one nonetheless; what is most striking is that the first theme of the first movement is virtually the same as that of Beethoven's sonata in the same key which happens to bear the same opus number, the so-called Hammerklavier Sonata.

The Rondo capriccioso, Op. 14, is of course one of Mendelssohn's best-known piano works, but the enchanting set of Trois Fantaisies ou Caprices, Op. 16, is programmed as infrequently as the Sonata, and what a delicious little suite it is! The ecentral Presto, in particular, is characteristic of Mendelssohn in his "elfin" frame and the sort of music that gives pleasure even in a competent amateur performance.

It is a good deal more than mere competence, of course, that Alpenheim brings to these four works, and it is further to her credit that the literal meaning of "amateur" ("lover") does come to mind, for she seems to be savoring and sharing the music with the most genuine affection as well as the formidable dexterity the music demands. Philips has provided fine piano sound and enhanced the presentation with a reproduction of Mendelssohn's own 1829 watercolor of Durham Cathedral.