Unlike CSound and other languages for audio synthesis, HMSL is primarily a language for making music. As such, it interfaces with sound-making devices through built-in MIDI classes. However, it has a high degree of built-in understanding of music performance practice, tuning systems, and score reading. Its main interface for the manipulate of musical parameters is through the metaphor of shapes, which can be created, altered, and combined to create a musical texture, either by themselves or in response to real-time or scheduled events in a score.
HMSL has been widely used by composers working in algorithmic composition for over twenty years. In addition to the authors (who are also composers), HMSL has been used in pieces by Nick Didkovsky, The Hub, James Tenney, Tom Erbe, and Pauline Oliveros.