1. https://www.zophar.net/music

2. https://downloads.khinsider.com/

3. https://cirrusretro.com/

4. https://vgm.hcs64.com/ (Requires foobar2000 and several console plugins to play the format for each game you downloaded)

5. https://www.woodus.com/forums/topic/33991-dragon-quest-warrior-discography-music-soundtrack-collection/ 
(Dragon Quest / Warrior - Discography - Music Soundtrack Collection)

6. https://project2612.org/list.php

7. https://www.vizzed.com/videogamemusic/