dmg half-speed crystal oscillator
this crystal oscillator will allow the nintendo® game boy® dmg/classic model to run at half-speed, resulting in a lower range of sounds capable of being produced (lowers notes by one octave).
crystal value is 2.097152 MHz, so half the speed of the factory installed crystal oscillator. this crystal oscillator is manufactured by fox (a reputable company for oscillators).
the crystal is non-polar, so the leads (legs) can be installed onto the circuit either direction you wish (unlike some capacitors, for example, that are polarized and have + and -- leads).
simply remove the factory-installed crystal oscillator inside the dmg and replace it with one of these. because of the size of these crystals, they must be placed elsewhere inside the dmg's case (they are too tall to be soldered from where the factory-installed crystal oscillator was removed). a simple solution is to install the crystal with wires connecting it to the pcb, and then you can place it anywhere you like inside the dmg's case.
(product image is a stock photo and not the actual product, although it reflects the size of the crystal being sold)