Guitar is a fretted musical instrument that usually has six strings. The sound is projected either acoustically, using a hollow wooden or plastic and wood box (for an acoustic guitar), or through electrical amplifier and a speaker (for an electric guitar). It is typically played by strumming or plucking the strings with the fingers, thumb or fingernails of the right hand or with a pick while fretting (or pressing against the frets) the strings with the fingers of the left hand. The guitar is a type of chordophone, traditionally constructed from wood and strung with either gut, nylon or steel strings and distinguished from other chordophones by its construction and tuning.


A percussion instrument is a musical instrument that is sounded by being struck or scraped by a beater (including attached or enclosed beaters or rattles); struck, scraped or rubbed by hand; or struck against another similar instrument. The percussion family is believed to include the oldest musical instruments, following the human voice. The percussion section of an orchestra most commonly contains instruments such as timpani, snare drum, bass drum, cymbals, triangle and tambourine. However, the section can also contain non-percussive instruments, such as whistles and sirens, or a blown conch shell. Percussive techniques can also be applied to the human body, as in body percussion. On the other hand, keyboard instruments, such as the celesta, are not normally part of the percussion section, but keyboard percussion instruments such as the glockenspiel and xylophone (which do not have piano keyboards) are included. Percussion instruments are most commonly divided into two classes: Pitched percussion instruments, which produce notes with an identifiable pitch, and unpitched percussion instruments, which produce notes or sounds without an identifiable pitch.


Piano is a large keyboard musical instrument invented in Italy by Bartolomeo Cristofori. It has a wooden case enclosing a soundboard and metal strings, which are struck by hammers when the keys are depressed. The strings’ vibration is stopped by dampers when the keys are released and can be regulated for length and volume by two or three pedals. The word piano is a shortened form of pianoforte, the Italian term for the early 1700s versions of the instrument, which in turn derives from gravicembalo col piano e forte and fortepiano. There are two main types of piano: the grand piano and the upright piano. The grand piano is used for Classical solos, chamber music and art song and it is often used in jazz and pop concerts. The upright piano, which is more compact, is the most popular type, as they are a better size for use in private homes for domestic music-making and practice.


A keyboard instrument is a musical instrument played using a keyboard, a row of levers which are pressed by the fingers. The most common of these are the piano, organ, and various electronic keyboards, including synthesizers and digital pianos. Other keyboard instruments include celestas, which are struck idiophones operated by a keyboard, and carillons, which are usually housed in bell towers or belfries of churches or municipal buildings.

Today, the term keyboard often refers to keyboard-style synthesizers. Under the fingers of a sensitive performer, the keyboard may also be used to control dynamics, phrasing, shading, articulation, and other elements of expression—depending on the design and inherent capabilities of the instrument.

Another important use of the word keyboard is in historical musicology, where it means an instrument whose identity cannot be firmly established. Particularly in the 18th century, the harpsichord, the clavichord, and the early piano were in competition, and the same piece might be played on more than one. Hence in a phrase like “Mozart excelled as a keyboard player” the word keyboard is usefully noncommittal.


An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the power of a signal (a time-varying voltage or current). An amplifier uses electric power from a power supply to increase the amplitude of a signal. The amount of amplification provided by an amplifier is measured by its gain: the ratio of output to input. An amplifier is a circuit that can give a power gain greater than one.

An amplifier can either be a separate piece of equipment or an electrical circuit contained within another device. Amplification is fundamental to modern electronics, and amplifiers are widely used in almost all electronic equipment. Amplifiers can be categorised in different ways. One is by the frequency of the electronic signal being amplified; audio amplifiers amplify signals in the audio (sound) range of less than 20 kHz, RF amplifiers amplify frequencies in the radio frequency range between 20 kHz and 300 GHz, and servo amplifiers and instrumentation amplifiers may work with very low frequencies down to direct current. A further distinction is whether the output is a linear or nonlinear representation of the input. Amplifiers can also be categorised by their physical placement in the signal chain; a preamplifier may precede other signal processing stages, for example.


Stringed instruments are musical instruments that produce sound from vibrating strings when the performer plays or sounds the strings in some manner.

Musicians play some string instruments by plucking the strings with their fingers or a plectrum—and others by hitting the strings with a light wooden hammer or by rubbing the strings with a bow. In some keyboard instruments, such as the harpsichord or piano, the musician presses a key that plucks the string or strikes it with a hammer.

With bowed instruments, the player rubs the strings with a horsehair bow, causing them to vibrate. With a hurdy-gurdy, the musician operates a mechanical wheel that rubs the strings.

In most string instruments, the vibrations are transmitted to the body of the instrument, which often incorporates some sort of hollow or enclosed area. The body of the instrument also vibrates, along with the air inside it. The vibration of the body of the instrument and the enclosed hollow or chamber make the vibration of the string more audible to the performer and audience. The body of most string instruments is hollow. Some, however—such as electric guitar and other instruments that rely on electronic amplification—may have a solid wood body.





Professional audio, abbreviated as pro audio, refers to a category of high quality, studio-grade audio equipment. Typically, it encompasses sound recording, sound reinforcement system setup and audio mixing, and studio music production by trained sound engineers, audio engineers, record producers, and audio technicians who work in live event support and recording using audio mixers, recording equipment and sound reinforcement systems.


A DJ mixer is a type of audio mixing console used by DJs for two different purposes: some DJs use the mixer to make seamless transitions from one song to another when they are spinning a set at a dance club. Hip hop DJs and turntablists use the DJ mixer to play record players like a musical instrument and create new sounds. DJs in the disco, house music, electronic dance music and other dance-oriented genres use the mixer to make smooth transitions between different sound recordings as they are playing.