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Sound
Several of us were involved in early experiments with computer music editing and synthesis [Saun77], and it was a disappointment to us that the original Smalltalk-80 release failed to incorporate this vital aspect of any lively computing environment. We determined to right this wrong in the Squeak release.
Early on, we implemented access to the Macintosh sound driver. As the performance of the Squeak system improved, we were delighted to find that we could actually synthesize and mix several voices of music in real time using simple wave table and FM algorithms written entirely in Smalltalk.
Nonetheless, these algorithms are compute-intensive, and we used this application as an opportunity to experiment with using C translation to improve the performance of isolated, time-critical methods. Sound synthesis is an ideal application for this, since nearly all the work is done by small loops with simple arithmetic and array manipulation. The sound generation methods were written so that they could be run directly in Smalltalk or, without changing a line of code, translated into C and linked into the virtual machine as an optional primitive. Since the sound generation code had already been running for weeks in Smalltalk, the translated primitives worked perfectly the first time they ran. Furthermore, we observed nearly a 40-fold increase in performance: from 3 voices sampled at 8 KHz, we jumped to over 20 voices sampled at 44 KHz.
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