smartcookie says: Songs are supposed to inspire us because they should come from the songs in the bais hamikdash.
What makes you think the people who make jewish music have any better shot of achieving that if they make it up or they copy? from the fact that they use these tunes, it must be that these people think this was sung in the beis hamikdash.
DONT DISCREDIT SONGS, DISCREDIT PEOPLE!