ProKussion 15 Key Alto Glockenspiel with Wooden Resonating Chamber and Removable Keys (6 Extra Keys and 4 Beaters) The ProKussion Series Alto and Soprano Glockenspiel. The ProKussion Series Glockenspiels comes with removable keys. Colour coded keys, make it easy to learn tunes. Spare beaters are included. The 15 keys are positioned on a 4cm deep wooden resonating chamber which produces a bright, warm sound. A one page learning resource is included with instructions on how to play a number of well recognised tunes.