I personally dont generally attempt to categorize friends, platonic, or things like that. Its something new for me. I dont really have set rules on that kind of stuff.
In regards to the platonic thing, he may just feel uncomfortable talking about these things with you whether its platonic or not or he may just want to escape from that aspect of his life for awhile and you may be the escape. Here is the best example I can give. I spend alot of time with my son and when I am away I dont really talk about him much. Doesnt mean anything other then he is such an integeral part of my life that its nice to not be consumed with it all the time. Just let him bring up his GF when he needs to. As long as he isnt trying to hide it IMO things are fine.
Being a shy person I really do need a more comfortable atmosphere where things arent so much direct one-on-one at first until I can figure out what it is that will pull us together, not romantically, more just figuring out where that connection is and where it is that we enjoy each others company. The guitar thing may not be that setting right now, it seems like texting is one way you connect, try to find other ways in which you 2 can connect.
I have done this, find someone where I think their could be a further connection and then see where it goes from there. Something about you caught his eye and he is probably trying to figure out where exactly that connection is and in what ways he can map you into his life. I never actually knew what the word platonic was until someone signed my yearbook "purely platonic" and I had to look it up.
Uumlau had mentioned that feelings just are, if you try to limit them you will miss out on alot of shared experiences because you are attempting to limit a relationship based on a category. I will limit myself in certain ways, but platonic is not one of the things I have ever defined or try to limit. Not really even romantic has been defined, really its more along the lines of seuxal and the desire to take it to that level. Romantic is even fine with me as long as that setting doesnt cause any problems which for me would be a desire to take it past the romantic setting. I am confusing that way. If you can be in a romantic settings with people before you even define them as a girlfriend, why does platonic mean that these settings have to be excluded. Its actually entertaining to bring in romantic settings as it makes some uncomfortable because they have a predefined map of where these things will lead. The people I am actually the most comfortable doing this with are the ones who become uncomfortable because I know it wont go anywhere

Of course I have been told that I tend to flirt and play with those lines *ponders*
One other thing is that my wife had mentioned that may fit is that people can label things and that labels steers them in certain directions. As a person that doesnt generally label things I have more of a sliding scale and their are things above where people would label platonic and below where people label girlfriend. If you dont then there are experiences that you may miss out on that you enjoy.
Just my 2 cents.