I'm also solo.
But I made my games using my own graphics and musics. I'm also use the musics from other sources such as OpenGameArt and Incompetech.
Examples of the games I made with other's musics:
- Round Rotate (broken game, now hosted on GitHub) - Pinball Spring at Incompetech.com
- Aircrafter 2030 (my entry for the Construct 2030 jam) - Xeon Theme Remastered at OpenGameArt.org