10.7 [in development]: https://synthesiagame.com/forum/viewtop ... =9&t=10034
Standalone zip file:
10.6: https://cdn.synthesia.app/files/Synthesia-10.6.zip
10.5.1: https://cdn.synthesia.app/files/Synthesia-10.5.1.zip
10.5: https://cdn.synthesia.app/files/Synthesia-10.5.zip
10.4: https://cdn.synthesia.app/files/Synthesia-10.4.zip
10.3: https://cdn.synthesia.app/files/Synthesia-10.3.zip
10.2: https://cdn.synthesia.app/files/Synthesia-10.2.zip
10.1: https://cdn.synthesia.app/files/Synthesia-10.1.zip
10: https://cdn.synthesia.app/files/Synthesia-10.0.zip
9: https://cdn.synthesia.app/files/Synthesia-9.0.zip
8.6: https://cdn.synthesia.app/files/Synthesia-8.6.zip
8.5: https://cdn.synthesia.app/files/old_Synthesia-8.5.zip
8.4: https://cdn.synthesia.app/files/old_Synthesia-8.4.zip
0.8.3: https://cdn.synthesia.app/files/old_Synthesia-0.8.3.zip
0.8.2: https://cdn.synthesia.app/files/old_Synthesia-0.8.2.zip
0.8.1: https://cdn.synthesia.app/files/old_Synthesia-0.8.1.zip
0.8.0: https://cdn.synthesia.app/files/old_Synthesia-0.8.0.zip
0.7.5: https://cdn.synthesia.app/files/old_Synthesia-0.7.5.zip
0.7.4: https://cdn.synthesia.app/files/old_Synthesia-0.7.4.zip
0.7.3: https://cdn.synthesia.app/files/old_Synthesia-0.7.3.zip
0.7.2: https://cdn.synthesia.app/files/old_Synthesia-0.7.2.zip
0.7.1: https://cdn.synthesia.app/files/old_Synthesia-0.7.1.zip
0.7.0: https://cdn.synthesia.app/files/old_Synthesia-0.7.0.zip
0.6.5: https://cdn.synthesia.app/files/old_Synthesia-0.6.5.zip
0.6.4: https://cdn.synthesia.app/files/old_Synthesia-0.6.4.zip
0.6.3: https://cdn.synthesia.app/files/old_Synthesia-0.6.3.zip
0.6.2: https://cdn.synthesia.app/files/old_Synthesia-0.6.2.zip
0.6.1: https://cdn.synthesia.app/files/old_Synthesia-0.6.1.zip
0.6.0: https://cdn.synthesia.app/files/old_Synthesia-0.6.0.zip
Installer:
10.6: https://cdn.synthesia.app/files/Synthes ... taller.exe
10.5.1: https://cdn.synthesia.app/files/Synthes ... taller.exe
10.5: https://cdn.synthesia.app/files/Synthes ... taller.exe
10.4: https://cdn.synthesia.app/files/Synthes ... taller.exe
10.3: https://cdn.synthesia.app/files/Synthes ... taller.exe
10.2: https://cdn.synthesia.app/files/Synthes ... taller.exe
10.1: https://cdn.synthesia.app/files/Synthes ... taller.exe
10.0: https://cdn.synthesia.app/files/Synthes ... taller.exe
9.0: https://cdn.synthesia.app/files/Synthes ... taller.exe
8.6: https://cdn.synthesia.app/files/Synthes ... taller.exe
8.5: https://cdn.synthesia.app/files/old_Syn ... taller.exe
8.4: https://cdn.synthesia.app/files/old_Syn ... taller.exe
0.8.3: https://cdn.synthesia.app/files/old_Syn ... taller.exe
0.8.2: https://cdn.synthesia.app/files/old_Syn ... taller.exe
0.8.1: https://cdn.synthesia.app/files/old_Syn ... taller.exe
0.8.0: https://cdn.synthesia.app/files/old_Syn ... taller.exe
0.7.5: https://cdn.synthesia.app/files/old_Syn ... taller.exe
0.7.4: https://cdn.synthesia.app/files/old_Syn ... taller.exe
0.7.3: https://cdn.synthesia.app/files/old_Syn ... taller.exe
0.7.2: https://cdn.synthesia.app/files/old_Syn ... taller.exe
0.7.1: https://cdn.synthesia.app/files/old_Syn ... taller.exe
0.7.0: https://cdn.synthesia.app/files/old_Syn ... taller.exe
0.6.5: https://cdn.synthesia.app/files/old_Syn ... taller.exe
0.6.4: https://cdn.synthesia.app/files/old_Syn ... taller.exe
0.6.3: https://cdn.synthesia.app/files/old_Syn ... taller.exe
0.6.2: https://cdn.synthesia.app/files/old_Syn ... taller.exe
0.6.1: https://cdn.synthesia.app/files/old_Syn ... taller.exe
0.6.0: https://cdn.synthesia.app/files/old_Syn ... taller.exe
Oldest versions(Alpha)
0.5.1: https://sourceforge.net/projects/pianoh ... ame/0.5.1/
0.5.0: https://sourceforge.net/projects/pianoh ... ame/0.5.0/
0.4.0: https://sourceforge.net/projects/pianoh ... ame/0.4.0/
WARNING: Downloading these alpha versions comes at a risk: Do not bring these files close to Activision. You (or npiegdon) will probably get into some sort of thing. Now, I don't know what that thing is, but I don't want to be called out for not warning them if something DID happen.
You could use Archive.org, but if you want versions older than 8.4 it won't work because the download button redirects to the 8.4 link. Literally. (it's because of the old_ naming in the links and 8.4 is the earliest that doesn't have that)
(0.5.1, 0.5.0, and 0.4.0 got removed from the CDN. Learn More)
I couldn't find any earlier versions, but this is already way back! Bye!

Also, this post is not only for now, but for the future when these later versions become unavailable to download on the Synthesia website.
I will check on this post every month to update it when and if new versions of Synthesia are released.
(I kinda want this topic to be stickied)