Welcome to The Bird Song Data
The Macaulay Library at Cornell is the go-to source for galapagos finch song data.
BirdWeb has a song lirary that is extensive by way of North American birds, but not so much Galapagos finches.
I Found an a song base from Arizona Field Ornithology. This is the link to the finch tag, which is labeled “Fringillidae – Finches and Goldfinches” which I’m not sure is one of the species we are interested in.
I’m having some trouble finding info on galapagos finches specifically, I have another link to bird song but its again mostly house finches.