Aston Magna is coming to Washington. The foundation, located in Great Barrington Mass., is headed by Albert Fuller, harpsichordist. On Monday at 8:30 p.m., Fuller will join with soprano Carole Bogard; John Solum, flute: and Stanley Ritchie, David Miller and Fortunato Arico on violin, viola and cello, in music by Duport, Veracini, Bach, Mozart and Handel. The program will be played in the Smithsonian Hall of Musical Instruments.

Fuller, who was born in Washington, sang in Washington Cathedral Choir, played a stunning organ recital there some years ago and then gave up the larger instrument to become one of the leading harpsichord virtuosos of our tune. He is now on the faculties of the Juilliard and Yale School of Music. Tickets for the Monday night concert are available through the Smithsonian Central Box and museum shops, and at Record Tape Ltd, 19th and L Street.

The Tel Aviv Strings, a chamber orchestra of 19 players from Israel, now on their first U.S. tour will play at 8:30 tonight in the Jewish Community Center in Rockville, Natasha Tatson will be the piano soloist with the group under the direction of Sholom Ronly-Riklis. Tickets are free to center members, $2 for non members, $1 fro students.

McNeil Robinson, organist of the Church of St. Mary the Virgin in New York City, will play a recital in St. Andrew's Episcopal Church in Arlington at 8 p.m. Wednesday.

At noon on Wednesday, the Washington Opera will present a discussion of Donizettis "Elisir d' Amore" in the South Atrium of the Kennedy Center. Free to Opera Guild members, tickets will be on sale to the general public. Talking about the opera will be soprano Catherine Maifitano stage director Arne Anderson, artistic administrator Francis Rizzo, and bass Gimi Beni.

Competitions: The National Symphony's contests for young artists will be held in January. The competitions are split into one for high school students and one for college students. The repertoire requirements are identical for each group, a matter for some conjecture. Details from Mrs. Donald C. May, chairman, 5931 Oakda'e Rd., McLean, 22101, or the NSO public relations office in the Kennedy Center, 795-8100.

The Friday Morning Music Club International Competition is now 25 years old. It is hard to believe , but the uncoming contest, in April, will be the club's 25th. This time again it will be for pianists with prizes totaling $3,500. Details from Mrs. Theodore Wemlsey, 8121 Rayburn Rd., Washington 20034.

A new idea in competitions: Gunther Kaunzinger, organist of the Shrine of the Immeculate Conception, is a specialist in the art of improvising.

Beginning Nov. 27, he will improvise the postlude following the noon Mass at the Shrine on themes submitted to him by members of the public, musicians or laymen. Anyone who wants to send Kauzinger a theme should mail it to Robert Shafer, music director, Shrine, Washington, D.C. 20017. Themes should be four to six measures long; it may be in any style. Those whose themes are chosen will be notified of the Sunday on which Kaunzinger will improvise on them.

Openings: The Washington Cathedral choir has openings for qualified tenors and basses. For auditions, call 966-3500 ext. 215, 216. And D.C. Community Orchestra has openings for experienced volunteer violinists and cellists. For details, call 362-5872 if you are a cellist; 622-0442 if you play violin.

Arthur Fielder opens the national Symphony's Pops Series Friday at 7 p.m. with Brian Ganz as soloist in the Prokofiev Third Piano Concerto.