The Timpani are sometimes called the Kettle drums, this is due to the familiar looking copper exterior. Unlike most drums when struck, they produce a definite (rumbling) pitch often used to enhance the texture of a piece.
(Numbers played in a concert: usually 2–4.)
Percussion instruments are struck, shaken, or scraped to produce a sound that either has a definite pitch (e.g. timpani) or that is unpitched (e.g. cymbals). The percussion section adds colour, tone, texture and rhythm to the music.
(Number played in a concert: usually 4-6.)
Most harps have 46 or 47 strings. The pedals, of which there are usually seven, are used to change the pitch by making the strings longer or shorter. Harps are played by plucking with the fingers.
(Number played in a concert: usually 1-2.)