Wolfram Research
Wolfram Math World: Calculus and Analysis
Over two dozen links are provided at this MathWorld site. From Polynomials and Series to Dynamical Systems and Catastrophe Theory, each link provides in-depth explanations and relevant diagrams of the topics at hand.
Other
Harmonic Analysis of Debussy's Prelude La Fille Aux Cheveux De Lin (Book I,viii)
A fine analysis of this Debussy prelude. Diagrams and text are easy to understand. The online sound clips are a plus! Site also available in Spanish.
Interactive Mathematics
Interactive Mathematics: Line Spectrum
Using Fourier and Harmonic series, the line spectrums of functions are derived and represented on graphs. Several music examples show the connection between harmonics and sound.
Interactive Mathematics
Interactive Mathematics: Harmonic Analysis
Derived from the Fourier series, the harmonic series can be used to represent even and odd functions. Definitions of second and third harmonics are also provided.