Excellent reading: Chapter 1 The Digital Representation of Sound, Part One: Sound and Timbre 1.1 What is Sound? 1.2 Amplitude 1.3 Frequency, Pitch and Intervals 1.4 Timbre Chapter 2 The Digital Representation of Sound, Part Two: Playing by the Numbers 2.1 The Digital Representation of Sound 2.2 Analog v. Digital