When green first launched there was research done on spells and songs. Proof was found that certain songs were not available in classic. If you look at
https://docs.google.com/spreadsheets...fSY/edit#gid=0 you will see that we get:
Shield of Song - November 2000 era
Niv's - February 2000 era
Solon's Bravura - April 2000
Jonthan's Provocation - April 2000