On Nabokov and Music, the top authority is Boris Katz.  Unfortunately, much of his work in this area is still in progress, and the things that have come out are in Russian.  They need to be translated--or everyone needs to learn Russian (I vote for number 2!  Help save a Russian program today--sign up for Russian courses!)

Here's one available on line; section 4 of the article is about music in Nabokov's The Gift.
http://magazines.russ.ru/voplit/2005/5/ka26-pr.html