Spectrograms are being used in musical compostion, in the technique called granular synthesis. Granular synthesis can be explained using some simple examples from spectrograms. In the spectrogram below we see just one point graphed in the time-frequency plane. Inverting this spectrogram produces the waveform shown below. If you listen to this waveform, by clicking the Play audio link, you will hear a single grain of sound.
By putting together these single points into a "picture" in the time-frequency plane (a set of grains) and then inverting, we obtain a more complec sound waveform by "granular synthesis." For example, we show in the figure below a spectrogram obtained by plotting a basic figure (a parabolic arc linked to two line segments on the left, obtained as a simple schematic diagram of an oriole's chirp shown on the right) and then shrinking and translating it several times. This repetition of time-frequency structure at multiple time-scales should (by our basic musical theory described in Hierarchical structures in music) produce a musical sound. In fact, if you listen to the sound waveform by clicking on the Play audio link, you will hear a reasonable facsimile of a bird song. (To produce a more human, instrumental, sound we would, at least, need to include overtones for timbral effects as shown in the next example.)
Oriole chirp 
A more human sounding musical effect is produced using granular synthesis - plus the music theory described in Hierarchical structures in music and in the preprint, Music: A time-frequency approach, as shown in the spectrogram drawn below. This spectrogram uses the fractal shape of Sierpinski's triangle for the fundamentals and includes overtones. See the preprint, Music: A time-frequency approach, for further discussion of how the granular synthesis was done. If you listen to the audio of the file, or watch the video, you will hear a succession of ghostly sounds, first ascending in scale and then descending. We call this short compostion, Sierpinski. (For a related composition, Sierpinski round, which employs a musical illusion, see the discussion of Shepard's tones.)
More examples
For more examples of granular synthesis, visit the Metasynth webpage at the link below. Metasynth is powerful software for performing granular synthesis. Some examples generated by electronic composers can be found at the second link below. Electronic music is still in its infancy, so not all examples will be to everyone's taste.
This
Web Page Created with PageBreeze
Free Website
Builder