A controller keyboard, also known as a MIDI keyboard, is a type of MIDI controller that resembles a traditional piano keyboard. It typically has a range of full-size velocity-sensitive keys, and may also include other controllers such as knobs, sliders, and buttons. These can be used to control various aspects of the sound, such as the volume, pitch, and modulation. Controller keyboards are typically used in music production and performance, allowing musicians and producers to control and manipulate a wide range of virtual instruments, samples, and sound effects using a single, intuitive interface. They can be used with a computer and music production software, or with a sound module or synthesizer. Some controller keyboards also have built-in sound engines, allowing them to produce sound on their own. Controller keyboards come in various sizes, from 25-key to 88-key, and they can also come with or without after touch, which is an additional pressure sensitivity on the keys, allowing a more expressive control of the instrument.