Keyboard amplifier in the context of Electronic keyboard

Audio crossovers are a type of electronic filter circuitry that splits an audio signal into two or more frequency ranges, so that the signals can be sent to loudspeaker drivers that are designed to operate within different frequency ranges. The crossover filters can be either active or passive. They are often described as two-way or three-way, which indicate, respectively, that the crossover splits a given signal into two frequency ranges or three frequency ranges. Crossovers are used in loudspeaker cabinets, power amplifiers in consumer electronics (hi-fi, home cinema sound and car audio) and pro audio and musical instrument amplifier products. For the latter two markets, crossovers are used in bass amplifiers, keyboard amplifiers, bass and keyboard speaker enclosures and sound reinforcement system equipment (PA speakers, monitor speakers, subwoofer systems, etc.).

Crossovers are used because most individual loudspeaker drivers are incapable of covering the entire audio spectrum from low frequencies to high frequencies with acceptable relative volume and absence of distortion. Most hi-fi speaker systems and sound reinforcement system speaker cabinets use a combination of multiple loudspeaker drivers, each catering to a different frequency band. A standard simple example is in hi-fi and PA system cabinets that contain a woofer for low and mid frequencies and a tweeter for high frequencies. Since a sound signal source, be it recorded music from a CD player or a live band's mix from an audio console, has all of the low, mid and high frequencies combined, a crossover circuit is used to split the audio signal into separate frequency bands that can be separately routed to loudspeakers, tweeters or horns optimized for those frequency bands.

A digital piano is a class of electronic keyboard or synthesizer (rompler) designed to serve primarily as an alternative to the traditional acoustic piano, both in how it feels to play and in the sound it produces. Digital pianos use either synthesized emulation or recorded samples of an acoustic piano, which are played through one or more internal loudspeakers. They also incorporate weighted keys, which recreate the feel of an acoustic piano. Some digital pianos are designed to also look like an upright or grand piano. Others may be very simple, without a stand.

While digital pianos may sometimes fall short of acoustic ones in feel and sound, their advantages include being smaller, weighing much less, and costing less than an acoustic piano. In addition, they do not need to be tuned, and their tuning can be modified to match the tuning of another instrument (e.g. a pipe organ). Like other electronic musical instruments, they can be connected to an amplifier or a PA system to produce a sound loud enough for a large venue or, at the other extreme, may be heard through headphones only. Some digital pianos can emulate other sounds besides the piano, the most common ones being pipe organ, electric piano, Hammond organ, and harpsichord. Digital pianos are often used in music schools and music studios as a replacement for traditional instruments.

Musical Instrument Digital Interface (/ˈmɪdi/; MIDI) is an American-Japanese technical standard that describes a communication protocol, digital interface, and electrical connectors that connect a wide variety of electronic musical instruments, computers, and related audio devices for playing, editing, and recording music. A single MIDI cable can carry up to sixteen channels of MIDI data, each of which can be routed to a separate device. Each interaction with a key, button, knob or slider is converted into a MIDI event, which specifies musical instructions, such as a note's pitch, timing and velocity. One common MIDI application is to play a MIDI keyboard or other controller and use it to trigger a digital sound module (which contains synthesized musical sounds) to generate sounds, which the audience hears produced by a keyboard amplifier. MIDI data can be transferred via MIDI or USB cable, or recorded to a sequencer or digital audio workstation to be edited or played back.

MIDI also defines a file format that stores and exchanges the data. Advantages of MIDI include small file size, ease of modification and manipulation and a wide choice of electronic instruments and synthesizer or digitally sampled sounds. A MIDI recording of a performance on a keyboard could sound like a piano or other keyboard instrument; however, since MIDI records the messages and information about their notes and not the specific sounds, this recording could be changed to many other sounds, ranging from synthesized or sampled guitar or flute to full orchestra.

A sound module is an electronic musical instrument without a human-playable interface such as a piano-style musical keyboard. Sound modules have to be operated using an externally connected device, which is often a MIDI controller, of which the most common type is the musical keyboard. Another common way of controlling a sound module is through a sequencer, which is computer hardware or software designed to record and playback control information for sound-generating hardware. Connections between sound modules, controllers, and sequencers are generally made with MIDI (Musical Instrument Digital Interface), which is a standardized interface designed for this purpose.

Sound modules are often rack-mountable, but are also produced in table-top form factor, particularly when the intended user is a DJ or record producer. The height of a sound module is often described in rack units. Small sound modules are mostly 1U in height, the larger models a multiplication e.g. 2U or 3U. Despite their name, most sound modules do not produce any audible sound until their output is plugged into a keyboard amplifier or a PA system.

A stage piano is an electronic musical instrument designed for use in live performances on stage or in a studio, as well as for music recording in Jazz and popular music. While stage pianos share some of the same features as digital pianos designed for home use and synthesizers, they have a number of features which set them apart. Stage pianos usually provide a smaller number of sounds (usually acoustic piano, electric piano, and hammond organ), with these being of higher quality than the ones found on regular digital pianos and home synthesizers.

Unlike many digital pianos, which are designed for semi-permanent installation in a private home and have design elements which make regular transportation difficult (e.g., permanently mounted legs, modesty panel, internal power amplifier and speakers, and a fixed sustain pedal), a stage piano generally has a portable, detachable stand, no internal amp or speakers (an output jack is provided so the instrument can be plugged into a keyboard amplifier), a detachable sustain pedal to be plugged into a jack, and a robust body. This enables a performer to remove all of the detachable parts and makes the instrument easier to transport to gigs and rehearsals.