what is the difference between good and bad music


my friend says rap is bad music. another friend says mahler is a terrible composer.

is it all subjective, i.e., a matter of opinion ? or are there standards which can distinguish good from bad music, however one defines these terms ?

if there are standards, can one specify them or refer me to a source ?
mrtennis
Beauty is truly in the eye (or ear) of the beholder. What moves your heart? I enjoy everything from Miles to The Pixies from Delibes to The Beastie Boys. It runs the gamut at our house. Enjoy!
Kthomas:

I could send you the list of my music collection - it's pretty definitive as to what is good music. Some people disagree with me, but they're just idiots.

That made me burst out in laughter, thanks.
Good music moves the soul and engages the mind. Bad music is annoying, or worse, unimportant to the listener--just as hate is not the opposite of love, indifference is the opposite of 'like' or acceptance in this context.
Think Mozart's work,and though completely disparate, Nat King Cole, Cannonball Adderly, Nancy Wilson, Mundel Lowe, Ella Fitzgerald, Dean, when serious, and now, a current favorite of mine Michael Buble, who is not only talented but a great showman to be so young.
Better recordings don't hurt our impressions of what we perceive to be 'good or bad'.
Music is art--Monet is brilliant if you love deep rich colors--some of the Dutch if you like perceived photo like clarity of some of their facial works, (now, though debatably, done with mirrors and 'tracing'. But who cares, it's marvelous to me.
The beholder can be vastly overrated when it comes to relative taste. But the audience makes these decisions with their money. IMHO
Good music is every CD in our collection. Bad music is what my parents think of it.