This is the week National Symphony subscribers will welcome back Antal Dorati to the orchestra's Tuesday, Wednesday and Thursday concerts. Now music director of the Detroit Symphony, where he opened the season to sold-out houses for a Beethoven festival, Dorati returns to the scene of his triumphs with the National Symphony as its principal guest conductor. He will be back again in the spring for several weeks.This week his music will be by Bach, Beethoven and Brahms.

It is again MESSIAH time around the world. In the Washington area the following scheduled for the coming weeks: (For particular information check with your church or school or other likely "Messiah" producers.)

The National Symphony's annual go at Handel's biggest hit will be heard under the baton of Robert Shaw, one of the world's famous specialists in this work. He will conduct it on Dec. 8,9,10 and 11, with the Choral Arts Society and soloists Haywood, Kopleff, Tucker and Plishka. Since these are non-subscription performances, all seats in the Kennedy Center are on sale. The Sunday performance will be at 3 p.m., the others at 8:30. All four will be complete.

The GWU chorus and orchestra, conducted by Stephen Prussing, will give its annual "Messiah" at 8 p.m. Dec. 1 in Lisner Auditorium Free, Southern Maryland's Choral Society, under Sandra Willetts, will do the Christmas portion only on Dec. 3 at 8 p.m. in Good Shepherd Methodist Church. Waldrof, Md.: Dec. 4 at 8 p.m., Publick Playhouse, Hyattsville, Md.; Dec. 10 at 8 p.m., Old Oxon Hill High Auditorium; and Dec. 11 at 8 p.m., Bethany Christian Church, Camp Springs, Md.

Choirs and choral groups from northern Virginia will send time on Dec. 4 in a "Messiah Sing-In" at 3 p.m. in Potomac Baptist Church, Sterling, Va., followed by a complete performance at 7:30 p.m., same place, with organ, harpsichord, timpani and all the choristers. For details on this one, call 323-4527.

The Alexandria Symphony Orchestra and combined choruses under George Steiner will sing the Christmas portion of "Messiah" plus "selected portions of the remainder of the work" Dec. 10 at 8:30 p.m. in T.C. Williams Auditorium, Alexandra.

NON-MESSIAH: Area chapters of the American Guild of Organists are putting on a Baroque Weekend Dec. 2, 3 and 4. There will be lecture demonstrations on keyboard and choral practice in Bach's time, with a final concert Dec. 4 at 5 p.m., in Augustana Lutheran Church, New Hamshire and V Sts., NW, of Cantata No. 61.

The 8 p.m. lecture Dec. 2, and those at 10 a.m., 1, 2:30 and 4 p.m. Dec. 3, as are open to the public for a charge. The closing Vespers at Augustana Lutheran is free.

For further details of the weekend, call 332-4010.