Two application guides (Tone generation and Melody player) from Microchip to get you started on tone generation basics, these might help create musical greeting cards to give to your fellow geeks this coming holidays.
A general purpose resonator routine is implemented using a PIC17C42. This routine is used to generate multiple tones. A tone signal is normally generated using extensive table lookup schemes.When a multiple tone signal is desired, each tone must have its own lookup table, thus requiring a large amount of storage space, especially when various frequencies are to be generated. This application note implements tone generation using recursive techniques.