The celesta, invented in 1886 by Auguste Mustel, is a
keyboard instrument resembling a small upright
piano. The keys control a series of hammers which strike against metal bars fastened over
wood resonators. It is like a keyboard version of the
glockenspiel, though the sound is softer; both instruments are known as
metallophones. It has a very delicate and
ethereal tone, and this most likely inspired its name which is from the French word
céleste, meaning celestial.
It can add a wonderfully magical colour to the orchestra as in the infamous 'Dance of the Sugar-Plum Fairy' in Tchaikovsky's 'The Nutcracker' which is considered its first major role in a large orchestral work.
Its music is written on two staves in the treble and bass clefs, like the piano. It has a four-octave range and sounds an octave higher than the written notes.
Even as an orchestral instrument it is a rarity, however, here are two examples in which it is used:
Béla Bartók: Music for Strings, Percussion and Celesta.
Shostakovich: Ballet suite No. 1, "Music Box Waltz"