A sampler is an electronic musical instrument that records and plays back samples (portions of sound recordings). Samples may comprise elements such as rhythm, melody, speech, sound effects or longer portions of music.

The mid-20th century saw the introduction of keyboard instruments that played sounds recorded on tape, such as the Mellotron. As technology improved, cheaper standalone samplers with more memory emerged, such as the E-mu Emulator, Akai S950 and Akai MPC.

Samples may be loaded or recorded by the user or by a manufacturer. The samples can be played back by means of the sampler program itself, a MIDI keyboard, sequencer or another triggering device (e.g., electronic drums). Because these samples are usually stored in digital memory, the information can be quickly accessed. A single sample may be pitch-shifted to different pitches to produce musical scales and chords.

Often samplers offer filters, effects units, modulation via low frequency oscillation and other synthesizer-like processes that allow the original sound to be modified in many different ways. Most samplers have Multitimbrality capabilities – they can play back different sounds simultaneously. Many are also polyphonic – they are able to play more than one note at the same time.

Prior to computer memory-based samplers, musicians used tape replay keyboards, which store recordings on analog tape. When a key is pressed the tape head contacts the moving tape and plays a sound. The Mellotron was the most notable model, used by a number of groups in the late 1960s and the 1970s, but such systems were expensive and heavy due to the multiple tape mechanisms involved, and the range of the instrument was limited to three octaves at the most. To change sounds a new set of tapes had to be installed in the instrument. The emergence of the digital sampler made sampling far more practical.

The earliest digital sampling was done on the EMS Musys system, developed by Peter Grogono (software), David Cockerell (hardware and interfacing) and Peter Zinovieff (system design and operation) at their London (Putney) Studio c. 1969. The system ran on two mini-computers, Digital Equipment PDP-8's. These had a pair of fast D/A and A/D converters, 12,000 (12k) bytes of core memory (RAM), backed up by a hard drive of 32k and by tape storage (DecTape). EMS equipment was used to control the world's first digital studio (EMS London (Putney) Studio), and their earliest digital sampling was done on that system during 1971–1972 for Harrison Birtwistle's "Chronometer" released in 1975.

The first commercially available sampling synthesizer was the Computer Music Melodian by Harry Mendell (1976), while the first polyphonic digital sampling synthesizer was the Australian-produced Fairlight CMI, first available in 1979. These early sampling synthesizers used wavetable sample-based synthesis. The Fairlight CMI played and recorded low quality samples at 8-bit audio depth and 8–24 kHz sampling rate.

In 1981, Toshiba introduced the LMD-649 in Japan. It was an early digital sampler that played and recorded high quality pulse-code modulation (PCM) samples at 12-bit audio depth and 50 kHz sampling rate, stored in 128 KB of dynamic RAM. It was created by engineer Kenji Murata for Japanese electronic music band Yellow Magic Orchestra, who used it for extensive sampling and looping in their 1981 album Technodelic. The LMD-649 was also used by other Japanese synthpop artists in the early 1980s, including Chiemi Manabe and Logic System.