Lorca writes poems about the guitar because of Falla's influence? Isn't the guitar simply the instrument used in the music FGL was celebrating, the cante jondo? Would Lorca need to think about violins imitating guitars to use onomatopoeia in his poetry?
What is lacking in these analogies is parsimony. Go for the most obvious explanations first. Only then, if they don't work, do you complicate things. I swear he does something like this almost on every page.