Some Lite Background…
Spectral music is a compositional practice that employs the analysis of the sonic spectrum as its foundation. Spectralist composers often use FFT (fast fourier transform) to analyze the frequency domain of a signal, giving access to the distribution of spectral components.
Composers that predate the available analytic technology, such as Olivier Messiaen, Lou Harrison, Edgard Varese, and Henry Cowell, among many others, have all displayed special interest in addressing the spectrum and intonation of sound as a focal point.
just intonation vs equal temperament
A just intoned piece by Lou Harrison:
More on temperament:
An audio/visual example:
Notice how the higher lines get darker as the overtones get higher…
Gerard Grisey’s Partiels
Grisey is a famous French composer responsible for arguably the most important spectral piece , Partiels. Partiels is an 18 piece ensemble composition based on the analysis of a low E (E2) trombone note. You can hear how he expands and contracts the spectrum over the composition, all triggered by the attack of the implied fundamental.