Which instrument is known as the 'king of instruments'?

The pipe organ is known as the “king of instruments.” The nickname reflects the instrument’s extraordinary range, power, variety of tone colors, and ability to sustain sound for as long as its air supply continues.

A pipe organ produces sound by sending pressurized air through pipes controlled from one or more keyboards, called manuals, along with a pedalboard operated by the feet. Different ranks of pipes imitate or suggest the sounds of flutes, reeds, strings, and brass instruments. By combining stops, an organist can create anything from a soft solo line to an immense orchestral-like climax.

Pipe organs have long been associated with churches and cathedrals, but they are also found in concert halls, cinemas, universities, and public buildings. The instrument varies enormously in size: some have only a few stops, while major organs contain thousands of pipes and multiple manuals. A common mix-up is to answer “piano,” because the piano is sometimes called the king of instruments in informal writing, but the established classical nickname in this question refers to the pipe organ.