key

In music, describes any piece where the melodies and harmonies are based on the notes of a major or minor scale. For example, a piece in the key of C major uses mainly the notes of the C major scale, and the harmonies are made up of the notes of that scale. The first note of a scale is known as the tonic and is the note that tells us the name of the key.

Most music which uses this system (known as the key system or tonal system) does not remain in one key, but moves to related keys in a process known as modulation. This adds contrast and creates tension, which is relieved when the music returns to the ‘home’ or tonic key.

The term is also used for the lever on keyboard instruments, such as the piano or organ, which the player presses in order to produce a note; and for the levers on woodwind instruments which players press to cover the note holes beyond the reach of their fingers.

key

In cryptography, the password needed to both encode and decipher a file. The key performs a sequence of operations on the original data. The recipient of the encoded file will need to apply another key in order to reverse all the operations in the correct order. Current encryption techniques such as Pretty Good Privacy (PGP) make use of a public key and a secret one.

key

Small, flat, low-lying island, normally composed of sand, formed on a coral-reef platform. Keys usually reach just a couple of metres above high-tide level. Initially formed from reef debris, they become stabilized by vegetation growth, but always remain susceptible to erosion. Keys are most commonly found in the Gulf of Mexico, particularly off the south coast of Florida, and in the Caribbean (for example, the Abacos islands).