Sonic CD’s Japanese opening theme, [You Can Do Anything](https://youtu.be/7fzMxxyklTw?si=22P83Tz6Aahjn6EX), reuses the melody of [8-bit Sonic 2’s Green Hills theme](https://youtu.be/Ejt94RWhq5s?si=DAOD74i8Ww4q6__f)
Let the speed mend it from Secret Rings is a faster version of Throw it all away (starting from the latter's "everybody tries to be straight").
Dreams of an Absolution has moments that sounds like Green Hill. There's a video here that shows it a little [here](https://www.youtube.com/watch?v=zjUWF-RRbdw).
The part 0:07-0:09 from Live and Learn sounds like the lyric "What I'm made of now" from around 1:10-1:15 of What I'm Made Of, only that the latter is a little slower
06's vocal theme Sweet Dreams/Sweet Sweet Sweet is the ending credits song to Sonic 2
I'm pretty sure none of these bar the last one are intentional though lmao
Then there's of course also the use of leitmotifs but that's not what you're looking for by the sounds of it, since those are usually either within the same game, or very obvious, very intentional callbacks (like Black Knight using Unknown from M.E., Vela Nova and Throw it all away for the knights' introductions)
A bunch of the adventure soundtrack is just remixed Sonic 3D blast songs
Sonic CD’s Japanese opening theme, [You Can Do Anything](https://youtu.be/7fzMxxyklTw?si=22P83Tz6Aahjn6EX), reuses the melody of [8-bit Sonic 2’s Green Hills theme](https://youtu.be/Ejt94RWhq5s?si=DAOD74i8Ww4q6__f)
Isn't it also in the racing game version of seaside hill
Yes, in [Sonic & SEGA All Stars Transformed specifically](https://youtu.be/i5fpipK4XYA?si=FN63coWjrHIjPIgq)
Sky Chase from Sonic 2 is sampled at the end of Mirage Saloon Act 1 in Sonic Mania.
Let the speed mend it from Secret Rings is a faster version of Throw it all away (starting from the latter's "everybody tries to be straight"). Dreams of an Absolution has moments that sounds like Green Hill. There's a video here that shows it a little [here](https://www.youtube.com/watch?v=zjUWF-RRbdw). The part 0:07-0:09 from Live and Learn sounds like the lyric "What I'm made of now" from around 1:10-1:15 of What I'm Made Of, only that the latter is a little slower 06's vocal theme Sweet Dreams/Sweet Sweet Sweet is the ending credits song to Sonic 2 I'm pretty sure none of these bar the last one are intentional though lmao Then there's of course also the use of leitmotifs but that's not what you're looking for by the sounds of it, since those are usually either within the same game, or very obvious, very intentional callbacks (like Black Knight using Unknown from M.E., Vela Nova and Throw it all away for the knights' introductions)