There were curious motivations behind these works: Thomas Roseingrave issued an edition of 42 sonatas of Scarlatti (London, c. 1739) in competition with the 30 Essercizi published shortly before by their composer, Roseingrave's friend; a strange manifestation of friendship that would nowadays lead to litigation. Avison, a composer, arranger, improviser and manager of various concert series, bent on putting together programmes to suit all tastes (and thus bring in the punters) adapted music of others, amongst them Scarlatti. Roseingrave arranged the sonatas in his edition (in 17 'Suites', adding some movements of his own, Avison ordered 29 of the sonatas as four-movement string 'Concertos', selecting them carefully to give the impression of unity—and he also introduced some probably 'non-Scarlatti' movements, which he himself may have composed. But this was not all: Avison changed the character of some of the sonatas by transposing them or altering their tempos.
A few are easy enough to identify, but a few hours may be pleasantly passed in tracing the others—and frustratingly so in weeding out the 'whodunits'; in his liner-notes, Franzpeter Goebels (the harpsichordist) does not spoil the fun by identifying any of the movements, but I'll give you a small start—the final movement of Concerto No. 9 is Kk7, denuded of many of its life-enhancing ornaments. The Berlin Ensemble use modern instruments. Whilst they play quite stylishly, with plenty of energy, and are very cleanly recorded, the effect is often heavy for a body of five strings and harpsichord, and they whet the appetite for a complete set by players of lighter touch and slimmer lines, and whose vibrato does not impart a slightly old-fashioned feel; Trevor Pinnock and The English Concert show the way in their recording of Concerto No. 9 (Archiv (CD) 415 518-2AH, 1/86). I'd give them six out of ten or, as there is no other integral recording of these attractive works, maybe seven and a half.'