The glockenspiel is a percussion instrument consisting of tuned steel bars that are hit with a hammer. In the past the instrument was usually operated by keyboard, but this is now rare. It frequently supplies the bell sounds required in an orchestra or the sounds of hammers on anvils. It was famously heard in Handel’s “Saul” in 1738 (where it was called a “Carillon”) and has since been used in music by Mozart, Wagner, Vaughan Williams, Richard Strauss, William Walton and others, always to fine effect and with more serious intent than its name implies.
Its sound is similar to, though brighter than, that of its keyboard cousin, the celesta.
Reference: “The Grove Concise Dictionary of Music”