The recorder in G is an instrument a tone higher than the treble (alto) recorder. Its history began in the early Renaissance, and in fact we may say that in that period it was the main recorder. In the first half of the 16th century, almost any kind of instrumental family, and the recorder one as well, had only three sizes: Soprano (Descant), Tenor and Bass. The soprano was in G, the tenor in C, and the bass in F.

Here is an engraving from Sebastian Virdung's Musica getutscht und ausgezogen (Basle 1511), perhaps the first treatise that describes the recorder family:

After that the descant (soprano) recorder in C became common, the recorder in G continued to be used, especially in Italy, as an alternative to the treble recorder in F. So, there is plenty of music, both renaissance and baroque, that suits better the recorder in G rather than in F.

In Italy, treatises that talk about recorder always describe a recorder in G:

• Silvestro Ganassi, Opera intitulata Fontegara (Venice 1535);
• Aurelio Virgiliano, Il Dolcimelo (first half of the 17th century);
• Bartolomeo Bismantova, Compendio musicale (Ferrara 1677).

In particular, Bismantova drew a Baroque recorder in G in three pieces, calling it «Flauto italiano»:

Here is a list of compositions available on the site playable with recorders in G.