ABSTRACT
Some key mathematical concepts are incredibly useful in describing audio effects. Most introductory signal processing deals with linear, time-invariant systems, which includes audio effects like equalization, panning, gain and delay. Latency is critical in many audio applications since multiple performers aim to synchronize what they play, as well as synchronize the sound with what the audience see. There is a bewildering variety of audio effects, which makes any systematic classification of them particularly challenging. The combination of pitches into notes, chords and melodies constitute the harmonic aspects, and audio effects aimed at modifying harmony often analyze the high-level musical structure in the signal. Having control parameters depend on an audio signal is what defines an adaptive audio effect. For non-adaptive audio effects, all parameters that influence the processing are either fixed or directly controlled by the user. Adaptive digital audio effects, in contrast, use features extracted from the audio to control the signal processing.
