Timpani (sometimes called kettle drums) are drums that are made out of large bowls that are usually made of copper shaped by craftsmen, which after being tuned, have a skin-like material stretched over the top. This material used to be a type of vellum or treated skin, but modern drums use a synthetic material. This top section is known as the "drumhead". 
Timpani is an Italian word. It is also a plural of the word timpano. However timpano is rarely used in informal English. More often, a timpano is referred to as a drum, a timpani, or simply a timp. Someone who plays a timpani is called a "timpanist".

Difference from other drums
Timpani are different from other drums because they are tuned to certain musical notes. A timpanist will often describe the drum as being "in voice" (or out of voice, as the case may be) when it is correctly tuned. To play it, it is hit with a special drumstick or "timpani mallet". Other drums that are used in orchestras and bands make a sound rather than a note, and are not tuned. A player normally sits with a group of two, three or four timpani around him, which is why the name timpani is in the plural.

Brief history
Timpani were originally used in official bands. They can still be seen in the bands of the modern official as in the Household Cavalry of Queen Elizabeth II of the United Kingdom, in which the "kettle drums" (as they are called) are carried by large  drumhorses.(See picture below) In the 1700s timpani became popular in orchestral music, and can be heard in the music of Handel, Beethoven and other 19th century composers wrote music that needed the timpani. Nowadays all large orchestras have timpani, and some bands that play popular music use them as well.

Different ways timpani can be made

The drumhead 
A timpani drumhead, also called a timpani head, can be made out of two different things. Some are made out of animal skin, like calfskin or goatskin. Other ones can be made out of thick plastic. Because plastic heads are hard to break and do not cost as much as animal skin heads, they are used more often than animal skin heads. However, a lot of professional players prefer skin heads because they think that skin heads make a better sound when they are hit. The drumhead is stretched over the bowl of the timpani and held on by screws for tuning the timpani.

Tuning the timpani 
The screws that hold and tune the drumhead are called "tension rods". To tune the timpani, the "tension rods" can all be tightened or loosened. The timpani makes a higher sound if the tension rods are made tighter, and a lower sound if they are loosened. There are usually around seven tension rods on the timpani.

Machine timpani 
Tuning a timpani by turning every tension rod by itself can be very hard, so some timpani makers invented different ways to change the drum's pitch more quickly.

Chain timpani 
In a chain timpani, the tension rods are all attached to a chain. This chain is hooked up to a lever, and when a player moves the lever back and forth, it tightens and loosens all the screws at the same time to change the pitch of the drum.

Pedal timpani 
A pedal timpani is a timpani that uses a pedal to change its pitch. It is the kind of timpani that is used the most today. A player can push on the pedal to make the timpani play higher notes, or let the pedal come back up to play lower notes. There are three different kinds of pedal timpani:
 In a ratchet clutch system a player must pull back a lever called a clutch to release the pedal. Once the pedal is in the spot where the player wants it, they must push the clutch forward with their foot again to lock it in place.
 A balanced action system uses a spring that is attached to the pedal, which keeps the pedal in one spot until it is moved by a player. Since the pedal is not held in one spot by a clutch in a balanced action system, some people call it a floating pedal because it looks like the pedal is not held on by anything and is floating.
 In a friction clutch system, the pedal is held in one spot by a clutch, and the clutch is attached to a pole. When a player releases the clutch, the pole moves up and down as the pedal is pushed up and down.

Timpani mallets 

Timpani are played with a special kind of drumstick called timpani mallets. A player uses two mallets at a time when they play the drum. The two parts of the mallet are called the shaft and the head. The head is the part of the mallet that is shaped like a circle, and is the part that hits the timpani, and the shaft is the wooden part of the mallet that is held by a timpanist. A timpani mallet's head can be made out of many things, but is usually made out of a wood sphere that is covered with felt or a thin cloth. The shaft of the mallet is usually made out of wood, like hickory, cherry, or bamboo, but can also be made out of metal, like aluminum. Some timpani mallets do not have a felt head, and just have a wooden one. These mallets are sometimes used in classical and baroque music.

In the beginning of the 20th century, some mallets had shafts made out of whale bones and heads made out of sponges.

Techniques 
With a pedal timpani, a player can produce different sound effects using the pedals. Performing glissando on timpani demands switching the pedals. Glissando is generated by pressing the pedal during the vertebra. Furthermore it is possible to play glissando at any volume level up or down. For example, Alexander Rahbari, an outstanding Iranian-Austrian composer used glissando effect produced by switching timpani pedals in the opening of his piece, Persian Mysticism Around G, where the player moves from Bb up to C and then rolling down to G(see the timpani part on right below).

Related pages
 Drum
 Pedal (music)

References

Other websites 

 Timpani FAQ  by Dwight Thomas, Lead Timpanist, Omaha Symphony
 Video  of Stuart Marrs, chairman of the University of Maine music department, performing the March from Eight Pieces for Four Timpani

Drums