The Touch Board ships pre-programmed to trigger MP3 when touched and pre-installed with a microSD card containing the Audio Guide that helps you get started.
The microSD card size that ships with the Touch Board is 128MB. A 4 minute song track is approximately 4MB so you could fit up to 32 track on this 128MB card.
If you need a bigger card the Touch Board will work with any size micro SD card up to 32GB. Make sure your new SD card is formatted as FAT32.