A pair of melodicas are attached to a vest using velcro strips. A Coleman air mattress pump sits in a sling on the back of the vest and provides a constant supply of air. The pump can be powered by D-cell batteries or by the battery pack in the backpack.
The melodicas have been outfitted with internal microphones. These are electret mics commonly seen as lapel microphones. The alto melodica has two mics to evenly capture the wider range.
The brain of the RockBox is an Arduino UNO with a SparkFun MP3 Player Shield. The shield holds a MicroSD card that stores all of the tracks in MP3 format. It can also act as a MIDI decoder, which opens the possibility of making it act more like a traditional drum machine in the future. The Power Glove selects tracks and sends play/stop commands.
Power is provided by a 12v LiFePO4 battery. It is rechargeable, half the weight of a comparable sealed lead acid, and won’t catch fire or explode like a regular lithium ion. A few voltage regulators convert and distribute power to the various components of the backpack. The single battery pack replaced 2 D-cells, 8 AAs, 3 AAAs, 2 9volts, and 3 button cell batteries.
The current backpack is a heavily modified Fydelity. The built-in amp was replaced with a much more capable Dayton Audio DTA-2, and the tiny speaker enclosures were replaced with a single 12″ chunk of 3″ PVC pipe for improved bass response.
A wireless transmitter can send all of the audio to the nearest PA if the party demands it. The melodicas, microphone shades, and drum beats are all mixed in the backpack to make one clean interface to the outside world.