Dear Martyn
But before getting too bogged down, the earlier question was whether the chitarra spagnola might be included as a continuo instrument, even by Agazzari. You'll know 'Le stravaganze d'amore' of Corradi (Venice 1616). This is an early 17thcentury source from a Northern Italian source and comprises songs for 'uni, due et tre voci' with alfabeto for the 'Chitarra alla Spagnola' as well as tablature for 'Chitarrone'. This source shows that this chitarra spagnola was tuned in a nominal e' top course ie the larger instrument. Since it is only a few years after Agazzari it certainly suggests that the instrument was at least a possibility to be included in his 'etcetera' of basso continuo instruments even at such a relatively early date.
Agazzari was working in Rome and Siena, and probably the chitarra spagnuola was more widely known there around 1600. But Agazzari's 'Del sonare sopra il basso' is really about figured bass and counterpoint, and from how he describes the use of the 'ornamental' instruments it appears that the chordal style of the guitar is not within sight. I doubt if Agazzari would have considered the alfabeto of the guitar as a 'foundation', while the bass is not even performed on the guitar.
Lex
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