A sampler is an electronic or digital musical instrument which uses sound recordings (or "samples") of real instrument sounds (e.g., a piano, violin, trumpet, or other synthesizer), excerpts from recorded songs (e.g., a five-second bass guitar riff from a funk song) or found sounds (e.g., sirens and ocean waves). The samples are loaded or recorded by the user or by a manufacturer. These sounds are then played back by means of the sampler program itself, a MIDI keyboard, sequencer or another triggering device (e.g., electronic drums) to perform or compose music. Because these samples are usually stored in digital memory, the information can be quickly accessed. A single sample may often 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. History 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