THE FOLGER CONSORT, resident music ensemble at the Folger Shakespeare Library, specializes in "early music" -- a catchall term that covers five centuries of music-making in a bewildering variety of styles with texts in a half-dozen basic languages.

Near the modern extreme of the Folger's repertoire is the music of John Dowland and his contemporaries from the time of Queen Elizabeth and King James I. This period is known primarily as a golden age of the theater, but its musical output (often closely linked to the theater) was not far behind in quality or quantity.

Amid a host of names, the two composers who stand out are William Byrd and Dowland, who will be the subject of this weekend's concerts in the Folger Library. A previous concert devoted to this period, taped at a live performance in February, 1986, and just issued by the library in cassette form, shows that the Folger Consort is a world-class ensemble. The engineering, like the performance, is first-class.

A major attraction is the singing of soprano Ann Monoyios, who is tonally splendid and adopts an Elizabethan accent -- not unlike what you can hear today in Dublin. The instrumentalists support her singing superbly and, between vocal numbers, perform dances and fantasias from a period when instrumental virtuosity was just beginning to be one of music's charms.

THE FOLGER CONSORT --

"Dowland's Dances: Music from Elizabethan and Jacobean England" (audio cassette available from the Folger Shakespeare Library). Appearing Saturday through Monday night at the Folger Shakespeare Library.