"Words cannot speak of music and vice versa. It must be performed," Nadia Boulanger once said. Mlle. Boulanger was especially right about her own performance last Friday evening in the Fogg Museum--as close to a perfect evening of music as one could hope for.

The utmost efficiency consistent with impeccable elegance characterized the entire program--conducting, music, and performance. Mlle. Boulanger stood on her home ground: early and modern vocal and instrumental music. The selection of music avoided the Romantic period, and the blank from the death of Bach to the birth of Poulenc--1750 to 1899--accented the intellectualized, the carefully wrought, the finely spun. Inevitably, Mlle. Bouanger conceived and reaized the program in the image of her own precise character.

She conducts so parsimoniously that it would be easy to forget she is there: a little old lady in grey quietly paying out time on the tips of her fingers. When one hand tires, the other begins. Only at the ends of phrases and the entrances of the vocal ensemble does the underlying, steeled precision rise to the surface. She tapers and snubs the end of each phrase, each musical sentence. When one of the inner voices in the small vocal ensemble enters, she clears the air for it as if doing the breast-stroke. Like a fuse, she acts immediately in the moment of need; otherwise the music goes by itself--meaning, of course, that she is devilishly demanding at rehearsals.

The outstanding works in a program of nothing but major works came first and last. Bach's Cantata 161, 'Komm, du susse Todesstunde' (1715) matched the efficiency of Mlle. Boulanger's conducting with its extreme economy of harmonic movement and accompaniment. Under her restraint, the ensemble of some twenty singers and twenty instrumentalists managed to sound personal, even intimate. Tenor Karl Dan Sorenson filled the museum court-yard with his clear and accurate voice; in her second solo, Contralto Jenneke Barton did the same.

Carissimi's popular 'Historia de Jepthe' (1645) brought the program to a well-tailored conclusion. Major soloist for the evening, Marguerite Paquet (alto) gave the traditionally tenor Historious part an impressively smooth and certain performance. Mr. Sorenson again delivered a fine solo.

'A Blake Recitative' By Edwin Roxburgh (1937- ) received its first performance in the United States. For contralto solo (Miss Paquet) and small string ensemble, the work combined clearly defined theme and form with a lyric excitement and mobility. In that it exploited chromatic resources and non-traditional tensions, it was a modern work. It was carefully thought out and emotionally effective. Miss Paquet handled the difficult solo line with sureness; her performance showed that what might have been thought an unmusical vocal line really just expanded the meaning of lyricism.

A batch of madrigali, scherzi musicali, and canti amorosi by Claudio Monteverdi supplied the musical fun of the program. The vocal ensemble, especially tenori and bassi (as the printed program would have it), were in fine voice.

A more gallant place to hold such a concert than Fogg Museum would be hard to find: to suggest unblemished taste, few places would be better.

After all, Mlle. Boulanger was right. Words cannot speak of music. They can only suggest--hover on the periphery. You must hear Mlle. Boulanger yourself.