In the early days of DSPs (circa the mid ‘80s), audio compression and other audio algorithms really taxed the performance of the processors available at the time. And high-level language compilers for DSPs were, for the most part, lame. Therefore, real-time implementations of audio algorithms almost always required hand-optimized software. Now, 20 years later, processor performance has improved dramatically, and compilers are much better. So you might think the days of hand-tuning audio software are behind us.
They’re not.