This collection of files exists to serve you as starting point in exploring different sounds and how they're programmed in Sonic Pi.
Copy & Paste them into your Sonic Pi editor and start tweaking the values to change the sound.
The Sonic Pi integrated editor has a lot of keyboard shortcuts. A handy list of all shortcuts is integrated in the tutorial browser or online on github.
This image explains nicely, the four important parameters to controlling play
ed sounds in Sonic Pi.