The music for Lorca's plays, arranged by Lorca himself. was published in Spain in 1960, by the Unión Musical Española, in transcriptions by Gustavo Pittaluga. Pittaluga, a composer of Lorca's own Generation of 1927, consulted with Lorca's sisters, Concha and Isabel, and an actor, Santiago Ontañón, who essentially sang the music they remembered to him. The volume itself is a bibliographical rarity, but I was able to get one a few years back. Strangely, the book doesn't appear much in the secondary literature on Lorca and music. The book has a prologue by José Bergamín.
The songs appear recorded by Germaine Montero, a French singer. I don't know if she used this book, but she was recording with another composer, Bacarisse, who was also part of the Pittaluga group.
Some of the music consists of non-Lorca songs, that he put in his plays. Another category is songs for which he wrote the words, but used a pre-existing popular melody. Finally, there are songs that may be Lorca's own melodies. I can't say what these are, because I would have to know every possible melody in Spanish folklore to say a melody is NOT from Spanish folklore.
Anyway, Lorca and music is a huge topic, but it is still possible to find out new things.