Especially the popular music of those decades; any kind of timeline for western bands going over there for the first time would also be tremendously helpful? Even if you know of a source that only tackles one decade, that’s better than nothing. I’ll even take resources in Japanese, as long as it’s in a format that can be easily web translated.
https://www.reddit.com/r/japan/comments/11s02f3/where_can_i_learn_about_japanese_pop_culture_from/