The mp3 player 99.999999% uses MLC NAND flash in a 48 pin tssop package. There are a couple of varieties of MLC nand flash, but in all cases the controller needs to know about the various chips. The MMC interface (the bus taht goes between your nand and your controller) is a parallel interface - probably 8 data bits and the control lines. You can't just attach another chip to these nets and expect it to work. The controller needs to know which chip it's reading/writing from and when. Simply piggy backing (eg paralleling the flash) will put your mp3 player in a whole world of hurt even if you can manage to solder the tight 48 pin tssop package without bridging the existing memory (which will be very difficult). Think about it - you're going to get bus contention in a major major way if you try to do what you're saying. If you want to do what you're saying, you'd need to modify the hardware/firmware so that the controller has two chip select lines - one for each flash. The best bet (and one which has a good shot of working) is to REPLACE the existing flash with a higher density one. The controller can very likely handle the higher density with no problem. The pin out should be the same (double check though) for the higher density chip and you should be able to simply drop it in (if you ensure that you use the same type of MLC - some have dual CS lines some have single CS lines). In either case here, I hope you and your friend are good at soldering... Good luck and be sure to report back!

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