That just sounds like you're extraverted. I'm the opposite (introversion); large groups wear me down and I need to retreat to get that 'recharged' feeling.
In response to your OP stuff, I think that's just a symptom of modern/western life. With the internet (and worse, the smartphone which lets you take it with you EVERYWHERE), there is never a shortage of novelty. You become habituated to instant access to the new. I started working with this aspect with an electronics 'fast'... I unplugged everything for 3 days, and stuck to reading books, meditation, cleaning the house.. etc.
The mental-music thing is interesting to see spoken about; I was never sure if anyone else had something like it. I've had the 'internal ipod' stuck on since I was 14 or 15 and only just started to try and take back control of that piece of my attention. I've tried to combat that by limiting my music consumption to JUST when I can give it my full attention and really savor it; no more 'background listening.' The rest is just sheer mindfulness to notice when I've started mental playback, and then focusing attention elsewhere (like the immediate sound environment).