With a few jumper connections, the board will boot up in MIDI mode that will read 'classic' 31250Kbaud MIDI data on a UART pin and act like a synth/drum machine - there are dozens of built-in drum and sample effects.

By default, MIDI mode is not 'activated' - but its very easy to turn on. Start by soldering a jumper wire between GPIO1 pin and 3V on the shield and a wire from Digital #2 to the RX pin on the shield, see the two yellow wires here:

Now run File->Examples->Adafruit_VS1053->player_miditest

Upload to the Arduino + Shield and listen on the headphone jack for the Ocarina scale being played. You can check the datasheet for a list of all the instruments (there's a lot!)