For the free recordings, I recorded myself playing a Chinese instrument for the first file and drumming on its surface for the second.
I took an excerpt of a jazz rhythm track online.
The stimulus that I used for the two sections were light chirping and quacking of geese passing by. To emulate birds chirping, I played on the high pitches of a piano. For the geese, I scratched upon a rough surface.
I only used the synthesized sounds for this mix and manipulated them through audacity.