A concert by the Cambridge Society for Early Music is not the dull evening of piddling pedantry you might expect. Too many people think that so-called early music is of solely academic interest, but Erwin Bodky and his group are gradually convincing them of their error.

Bodky's group is essentially the same organization that previously called itself the Cambridge Collegium Musicum. The objective is the same: to give authentic performances of unfamiliar Seventeenth and Eighteenth Century music. The only difference is in the personnel, which is vastly improved over last year.

Wednesday night's concert, the second of three, began with a Concerto for violin, cello, and harpsichord by Couperin. Ruth Posselt, the new violinist, is the competent, unspectacular kind of performer who subordinates herself to the music at hand. Her easy-going interpretation was perfect for this comparatively light-weight work. 'Cellist Samuel Mayes, who appeared in all eight parts of the program, showed remarkable versatility. His tone was full and rich in the important solo sections, but in the later continuo passage he held himself down so that one could barely hear him over the harpsichord.

Couperin's Premier Lecon de Tencbres, sung by soprano Helen Boatwright, was not a total success. The music too often bore no relation tot he words (excerpts from the Book of Jeremiah.) Still, there were many powerful moments such as the final plea to Jerusalem, which is repeated five times with different treatment each time. Miss Boatwright may not have the strongest voice in the world, but it is clear and accurate, and she sang with real comprehension of the Latin text.

Loeillet's Sonata in C major featured Alfred Mann's flawless playing of the recorder. But the biggest applause-getter of the evening was the Sonata for 'cello and harpsichord by Francoeur. The piece is full of piquant melodies, and despite the intricate finger work, Mayes handles his unwieldly instruments as if it were the size of a small banjo.

Two selections by Handel, a violin sonata and a solo cantata, proved disappointing. They are undistinguished occasional pieces, quite flattering to one of the real geniuses of the age.

The program ended with a soprano aria and a violin concerto by the Leroy Anderson of the Eighteenth Century, Frederick Telemann. Lyrical and witty, it is easy to understand why such pieces were so popular in their day.