Three questions about sensual desire

**If music is a sensual desire , what's wrong with that?** Sensual desire is described as the first of the five hindrances. What I am a little perplexed by is the stance of Buddhism on the positive senses. For instance, if I desire to listen to a song, is the problem the desire, or the 'emotions and feelings' the song itself brings up? **Apart from sensual 'desire', what about just sensual 'enjoyment'?** If I just happen to walk by an area in which music is playing, and I find myself tapping my feet, or feeling really good; is this seen as a state we must abandon? I mean, if we never desired the music in the first place and it just happens to play around us, what is the harm in seeing the beauty in it? If someone offers us food, are we required to not enjoy our sense pleasures of it? **Isn't even metta meditation also a sensual desire?** Also, metta-meditation frequently uses people as objects of good-will and loving-kindness -- however, this is attaching sense pleasures to mental objects, which I thought are to be abandoned? How does metta-meditation even make sense in the context of Buddhism when the meditation cultivates 'positive' states from mental objects?