This isn't one for the dyed-in-the-wool authenticist. Steven Isserlis plays J.S. Bach's three gamba sonatas on the cello; the Handel Sonata (HWV364b) is for violin or oboe, but with Handel's handwritten note that gamba is an alternative; the figured bass in Scarlatti's Harpsichord Sonata Kk90 might imply the top line being intended for violin, so cello is but one more step away.
Fortunately, desiccated 'authenticity' has been supplanted by imaginatively experimenting performers supported by scholarly evidence: composers were game for anything that worked, from simple salesmanship—'for flute, oboe, violin or harpsichord'—to some remarkable transfers between distant media: violin to organ, concerto to choral Mass movement, and so on.
Both Scarlatti and Handel are most alluring. With Robin Michael's added cello on the bass line, they become real duo sonatas with discreet, though inventive and often witty, continuo harpsichord. In the Handel slow movements Isserlis indulges stylistically in spontaneous-sounding elaboration of the line, while the thrilling final Allegro of the Scarlatti Sonata is wonderfully fluent.
Isserlis's note express his delight at partnering harpsichord: that his cello is audible rather than, as so often, struggling against a piano. In the Bach gamba sonatas, two keyboard hands and cello creating a trio texture, the problem is reversed: forward cello constantly smothers the fast-decaying harpsichord, audibly placed further back. But the quiet, reflective Adagio of BWV1029 is breath-taking, as is the inspired addition of a chorale prelude, Ich ruf' zu dir, with sustained cello above flowing harpsichord semiquavers. I'd buy the recording for this alone—purists be blowed!