Pietro Millioni produced a lot of guitar music. At least it seems that way. Today, we only have a few surviving editions of his works, and each of them is a reprint. Millioni was Italian, and very little is known of him other than that.
In a 1627, Millioni released Quarta impressione del primo, secondo, et terzo libro d’intavolatura, a fourth printing of his first three books of guitar tablature. Along with it came a second printing of Millioni’s fourth book, and a first edition of his 5th book. Later, in 1635 Millioni released another book, but the extant copy is incomplete and what we do have appears to be a compilation of the 1627 works.
Millioni provides a preface in which he instructs students on how to play the the various chords indicated by alfabeto symbols. He is, however, a bit different from earlier composers. Instead of using letters higher in the alphabet (like P, etc.) to indicate higher position chords, Millioni chose to use a lower letter plus a number: what we could think of as an indication for a bar chord. Eg. play an a minor chord shape in fifth position.
Where Can I Get Pietro Millioni’s books?
Currently, Millioni’s extant works are held at the Civico Museo Bibliografico Musicale G. B. Martini in Bologna, Italy. No one is publishing modern or facsimile editions at the time of writing. There’s a good overview of all Millioni’s treatises