Gustav Leonhardt is second to none in knowledge of the ins and outs of the music of the Baroque. The great Dutch harpsichordist tends to be associated with Bach, but his energies extend to the music of many of Bach's predecessors and contemporaries also. At the Smithsonian last night, his recital spotlighted too lesser masters, Frescobaldi and Balbastre, whose more specialized styles contributed to the stream of influence that culminated in Bach. It concluded with a bach prelude, fugue and suite.

Playing with the freedom that only comes with ultimate control, Leonhardt reveled in the abandon of two Frescobaldi toccatas, and then set about exploring the more restrained intricacies of a canzone and two capriccios. On the fragile-sounding Italian harpsichord, the purely distilled mannerisms sounded etherally abstract.

For the more sensual and personal pieces by Balbastre, Leonhardt moved to the more brilliant Dulken instrument. These pieces from the very end of the Baroque period represent the ultimate development of the small programmatic movement.

Resisting a contemporary tendency toward rhythmically mechanical performances of Bach, Leonhardt endowed the concluding works with a flexibility that did not preclude energetic drive. It was a performance guaranteed to disappoint the faddist but to delight the serious Bach lover.