Instruments: whirly-tube in F♯, glockenspiel, crotales (two octaves), cello, and piano
↑ You spin it around. It makes sounds. Specifically, ones in its harmonic series, which in this case is F♯. Wikipedia has a short article about them.
This piece only uses 5 distinct pitches (and pitches integer numbers of octaves away): F♯, G♯, A♯, C♯, and E♮.
Download: MP3, PDF (Parts: Percussion, Cello, Piano), LilyPond (view source)
An arrangement/remix made using the program Pure Data. (Also it's faster.)
Synthesized version: MP3, Pd file
Instruments: string trio
The family Cathartidae contains vultures that live in the Americas, which are not closely related to the vultures that live elsewhere. This piece, however, is closely related to my previous vultures piece.
Download: PDF (Parts: Violin, Viola, Cello), MIDI, LilyPond
I took a class in computer music composition. In that class, I created a piece using the tools I had learned about there. (Yes, that is the notes of a Mario sound effect.)
Among the tools I used was one that turned pictures into sounds; inputs to this program include this picture that I drew in an art class and the System Error dialog from pre–Mac-OS-X Macintosh computers.
Instruments: trumpet, horn, trombone, tuba
...and a year later I audited a class in music analysis, which talked about analyzing music in terms of melody, harmony, rhythm, "sound" (i.e., timbre, dynamics, and anything else that doesn't fit into the other categories), and form (which in the textbook we were using was called "growth"). At the same time I was taking a geology class and learning about different types of rocks, like igneous and sedimentary. This piece is divided into five sections, each using primarily one aspect of music and describing one rock type or geologic process: sound lava, harmonic igneous, rhythmic sedimentary, melodic metamorphic, and growth remelting.
The word rock in the title only refers to the geological type of rock; it has nothing to do with the homonymous style of music.
Download: PDF (Concert-pitch score; Parts: Trumpet, French horn, Trombone, Tuba), MIDI, LilyPond