The aim and final end of all music should be none other than the glory of God and the refreshment of the soul. If heed is not paid to this, it is not true music but a diabolical bawling and twanging.
J. S. Bach (1685-1750), Glory and Honor: the musical and artistic legacy of Johann Sebastian Bach, Gregory Wilbur & David Vaughan, Cumberland House Publishing, 2005, p. 1
What Bach says of music goes for pretty much everything else too! And yes, there can still be good in music not written by Christians, because we still retain a remnant of the image of God, but in terms of anchoring and purpose, it's totally adrift.