CSound is a programming language which facilitates sound and composition creation. Though my group's course project will not create any audio output, we are still learning the basics of this tool. For this assignment, I created a synthetic nature composition that includes Douglas squirrels and bullfrogs.
I modeled the squirrel sound off of this video: http://www.youtube.com/watch?v=pCuywbDOrAU&feature=related. I was inspired to make this sound because one of these critters woke me up while camping last summer. To create it with CSound, I used frequency modulation (FM) synthesis, modulating a triangle wave with a sawtooth. The overall amplitude is shaped with a quick exponential rise and longer exponential fall, so that it is loudest only for a moment. This helped to give a squeaking sensation, though the final sound is more buzzy than squeaky.
In addition, I shaped the pitch over the course of the note with function 14 as well. For the bullfrog, I made this option an additional instrument parameter.
I made the bullfrog in a very similar manner to the squirrel. The primary difference is that I added harmonics (jittered slightly) to attempt to mimic the frog's fuller sound: http://www.youtube.com/watch?v=M02_dnl9zCA (I used the frog that begins around second 33)
My frog sound uses the clarinet function for its base since it is a more muted sound. I modulate it with a pulse, consistently throughout the entire call. I shaped the amplitude and pitch with a couple of linear envelopes to simulate the rise and fall of the frog's croak.
Like the squirrel, my bullfrog sound has a stubborn buzzy quality that marks it as highly synthetic.
Using GarageBand, I used my two sounds to make a composition in which a chorus of frogs and squirrels sing a song.