A little history …
The origin and history of the glockenspiel is sketchy.
In its early days, this instrumentwould have consisted of bells, then later a set of tuned metal bars, played first with a piano-like mechanism in the eighteenth century, and then with baquettes in the mid-nineteenth century.
This evolution is explained because the old instrument produced a rather harsh, metallic sound and did not allow for much variation in sound.
The glockenspiel is a idiophone instrument, meaning that, when struck, the material is sufficient on its own to produce sound. It therefore has no strings or membranes. Once emitted, the self-resonant sound sustains itself for some time.