1. A program written for DOS by Carl Raffa , will emulate a CD multichanger at least to the point of enabling the AUX audio inputs.
( Requires a Unilink -> Parallel port cable )
2. A program written in 'C'/Asm for the Microchip PIC16F877 micro , performing similar functions to Carl's program - written by me - Jimbo.
3. A recent project started by Simon Wood and available on SourceForge - GnuLink ( I think ) - which is an AUX in enabler written in assembler for a Microchip PIC16F84 microcontroller.
So if there are any keen electronics engineers out there who feel like building the devices - the software is already begun.
Cheers - and thanks for listening.