== Hardware setup ==
The SD card should be connected to the SPI port of the controller. The chip select pin from the card can be connected to any free digital pin, but if pin 4 is used on Arduinos you don't have to adjust the source code. Many shields with SD card support like Ethernet-Shield will work. You need pegel conversion circuits from 5V to 3.3V for most Arduinos (except those that run natively on 3.3V).
According your mode configuration, one or two pins are used for audio output. This pins can not be changed and are different between different Arduino boards. For ATmega168/328 based plattforms those are pins 9 and 10. For ATmega1280/2560 those are pins 44 and 45. For other plattforms look into the file SimpleSDAudio.h.