Hold music
The music my conversation partner hears when (s)he is put on hold on my iPhone (by pressing and holding the mute button for a few seconds), is this provided by my iPhone, or by my operator?
The logical follow-up question would be "can I change it?", but I can guess the answer to that one... 🙂
MacBook Pro 13" 2.26GHz (June 2009), Mac OS X (10.6.4), iPhone 4, Time Capsule 500GB, Airport Express, iPod shuffle 512MB, iPod nano 8GB