A sampler is an electronic musical instrument closely related to a synthesizer. Instead of generating sounds from scratch, however, a sampler starts with multiple recordings (or "samples") of different sounds, and then plays each back based on how the instrument is configured. Because these samples are usually stored in RAM, the information can be quickly accessed.
Unlike traditional digital audio playback, each sample is associated with a set of synthesis parameters, and can thus be modified in many different ways.
Usually a sampler is controlled from an attached music keyboard, or from an external MIDI source. Each note value input into the sampler then accesses a particular sample. Often, multiple samples are arranged across the musical range, and assigned to a group of notes. If keyboard tracking is enabled, then the sample is shifted in pitch by an appropriate amount. Each group of notes to which a single sample has been assigned is often called a keyzone, and the resultant set of zones is called a keymap. When a note value is input to the sampler, it looks at the value, and plays back the sample associated with that note baban.
For example, in Fig 1, a keymap has been created with four different samples. Each sample should be associated with a particular center pitch. The first sample (violin G2), is distributed across three different notes: g2, g#2, and a2. If a G2 note is received, then the sampler will play back the Violin G2 sample at its original pitch. If a G#2 is input, then the sampler will play the Violin G2 sample, except it will shift it up by a chromatic semitone. Likewise, an A2 will play back the Violin G2 sample a whole-tone higher. However, when the next note (Bb2) is input, the sampler will then select the Violin B2 sample, and play it a semitone lower than that sample's center pitch of B2.
In general, samplers can play back any kind of recorded audio, and most samplers offer editing facilities which allow the user to modify and process the audio, and to apply a wide range of effects, making the sampler a powerful and versatile musical tool.
At the bottom lie the samples. Samples are individual recordings of any imaginable sound. Each will have been recorded at a particular sample rate and resolution. It is convenient, if the sample is pitched, that a reference center pitch is included. This pitch indicates the actual frequency of the recorded note. Samples may also have loop points, that indicate where a repeated section of the sample starts and ends. This allows a relatively short sample to play endlessly. In some cases, a loop crossfade is also indicated, which allows for more seamless transitions at the loop point by fading the end of the loop out while simultaneously fading the beginning of the loop in.
The samples are arranged into keymaps, or collections of samples distributed across the range of notes. Each sample placed into a keymap region should then reference which note value will play back the sample at original pitch.
These keymaps are arranged into instruments. At the instrument level, additional parameters may be added to define how the keymaps are played. For example, filters can be applied to change the color, low frequency oscillators and envelope generators can shape the amplitude, pitch, filter, or other parameter. Instruments may or may not have multiple layers of keymaps. A multilayer instrument will be able to play more than one sample at the same time. Often each keymap layer has a different set of parameters, so that the input affects each layer differently. For example, two layers may have different velocity sensitivity, and thus a note with a high velocity may accentuate one layer over another.
At this level, there are two basic approaches to sampler organization. In a bank approach, each MIDI channel is assigned a different instrument. Multiple banks can then be stored to reconfigure the sampler.
A different, and more powerful approach is to associate each instrument with a patch number or ID. Then, each MIDI channel can be configured separately by sending patch change information to the individual channel. This allows much more flexibility in how the sampler is configured.
Samplers can be classified as phrase samplers or studio samplers. The latter term is informal, the former appears in the manufacturer's documentation.
Phrase samplers work with the philosophy of a drum kit. Each keymap spans only a single key and generally has a different sample put under it. For a studio sampler, this would require a large number of zones (61 to fill a regular keyboard), each with its own settings; and each keymap has to be programmed as spanning just one key. This is a lot of work, especially on older menu-driven hardware samplers. Using the phrase sampling approach simplifies this and makes a translation to another interface (such as the 16 pads on the Akai MPC series) easier; the fact that each pad is actually a note is hidden from the user. It also saves computing power as the sampling engine does not have to re-pitch each sample (there is no need for an anti-aliasing algorithm) - it only has to play it back. Since the user interface is simplified in general, it is also a more attractive option for live use.
Studio samplers work as described above with the keymapping system. It is assumed that the user wants to "spread out" a sample over a certain range of keys. This has certain side-effects. These are desirable - such as speeding up or slowing down drum loops, effectively turning a sampler into a digital turntable. In some cases this is not desired; when for instance not enough samples are taken of an instrument, the higher and lower parts of a keymap may sound unnatural, and the transition from one keymap to another may be too noticeable. For mimicking realistic instruments, the art is to make transitions as smooth as possible.
The format differs in obvious ways - studio samplers are available in 19" rack format, phrase samplers have a groovebox format; lightweight, easy to operate and carry.
The first commercially available sampling synthesizer was the Computer Music Melodian (1976). The first polyphonic digital sampling synthesiser was the Australian-produced Fairlight CMI which was first available in 1979.
Prior to computer memory-based samplers, musicians used tape replay keyboards, which stored recordings of musical instrument notes and sound effects on analog tape. As a key was pressed, the tape head would contact the tape and play a sound. The Mellotron was used by a number of groups in the late 60s and 1970s. Such systems were both expensive and quite heavy due to the multiple tape mechanisms involved. These same factors limited the range of the instrument to at most three octaves. If the user wished to change sound, they would often have to change out many tapes -- not practical in a live setting.
Modern digital samplers use mostly digital technology to process the samples into interesting sounds. The E-mu SP-1200 percussion sampler progressed Hip-Hop away from the drum machine sound upon its release in August 1987, ushering in the sample-based sound of the late 1980s and early 1990s. Later, Akai pioneered many processing techniques, such as Crossfade Looping to eliminate glitches and Time Stretch which allows for shortening or lengthening of samples without affecting pitch and vice versa. The limiting factors in the early days were the cost of physical memory (RAM) and the limitations of external data storage devices.
During the early 1990s hybrid synthesizers began to emerge that utilized very short samples of natural sounds and instruments (usually the attack phase of the instrument) along with digital synthesis to create more realistic instrument sounds. Examples of this are Korg M1, Korg O1/W and the later Korg Triton and Korg Trinity series, Yamaha's SY series and the Kawai K series of instruments. This made best use of the tiny amount of memory available to the design engineers.
The modern-day music workstation usually features an element of sampling, from simple playback to complex editing that matches all but the most advanced dedicated samplers. The primary difference is that the workstation also includes additional features such as a sequencer to provide flexibility for composers.
Samplers, together with traditional Foley artists, are the mainstay of modern sound effects production. Using digital techniques, various effects can be pitch-shifted and otherwise altered in ways that would have required many hours when done with tape.
The Melodian was based on the Digital Equipment Corporation PDP-8 computer and hand wired D/A and A/D conversion and tracking anti-aliasing filters. The Melodian was first used by Stevie Wonder in the "Secret Life of Plants" (1979). The Melodian was a monophonic synth with 12 bit A/D and sampling rates up to 22 kHz. It was designed to be compatible with analog synthesizers and had a feature where it would sync to the pitch of an analog synth, such as an Arp 2600. This means the Melodian captured all of the frequency modulation effects, including the touch ribbon control. It also could trigger of the ARPs keyboard so it could almost be thought of as a hybrid sampler/analog synth, making best use of the technology that was available at the time.
The Fairlight CMI or Computer Music Instrument, released in (1979), started life as the QASAR M8. The M8 was handwired and legend has it that it took 2 hours to boot up. The CMI was the first commercially available digital sampling instrument. The original Fairlight CMI sampled using a resolution of 16 bits per sample at a rate of 24kHz, and used two 8-bit Motorola 6800 processors (later upgraded to the more powerful 16/32-bit Motorola 68000). It was equipped with two six-octave keyboards, an alphanumeric keyboard, and an interactive video display unit (VDU) where soundwaves could be edited or even drawn from scratch using a light pen. Software allowed for editing, looping, and mixing of sounds which could then be played back via the keyboard or the software-based sequencer. It retailed for around US$25,000.
Fairlight later released the Series IIx, which increased the sampling rate to 32kHz and was the first to feature basic MIDI functionality. In 1985, the Series III was released, adding support for SMPTE time code. Notable users of the Fairlight CMI include Peter Gabriel, Trevor Horn, Art of Noise, Yello, Pet Shop Boys, Jean Michel Jarre,and Kate Bush.
E-mu Emulator (1981) was E-mu Systems initial foray into sampling, and saved the company from financial disaster after the complete failure of the Audity due to a price tag of $70,000. The name 'Emulator' came as the result of leafing through a thesaurus and matched the name of the company perfectly. The Emulator came in 2-, 4-, and 8-note polyphonic versions, the 2-note being dropped due to limited interest, and featured a maximum sampling rate of 27.7 kHz, a four-octave keyboard and 128 kB of memory.
E-mu Emulator II (1985) was designed to bridge the gap between the Fairlight CMI and Synclavier and the Ensoniq Mirage. It featured 8 notes polyphony, 8-bit sampling, 512kb of RAM (1mb in the EII+ though only accessible as two independent 512kb banks), an 8-track sequencer, and analog filtering. With the addition of the hard disk option, the Emulator II was comparable to samplers released 5 years later.
E-mu Emulator III (1987) was a 16-bit stereo digital sampler with 16-note polyphony, 44.1 kHz maximum sample rate and had up to 8 MB of memory. It featured a 16 channel sequencer, SMPTE and a 40 MB hard disk.
E-mu SP-1200 was, and still is, one of the most highly regarded samplers for use in hip-hop related production. Its 12-bit sampling engine gave a desirable warmth to instruments and a gritty punch to drums. It featured 10 seconds of sample time spread across four 2.5-second sections.
E-mu Emax, sold between 1985 & 1995, and aimed at the lower end of the market.
E-mu ESI-32 (1994) was a stripped down, far cheaper, and simplified EIIIx, and could use the same samples. The unit could accommodate up to 32 MB RAM. 32 note polyphony and sounds could be routed internally to one of four polyphonic outputs. Via optional SCSI interface, the ESI-32 could access external CD-ROM, Zip-100, and hard drives.
Akai entered the electronic musical instrument world in 1984 when Roger Linn, the creator of the Linn LM-1, the Linn 9000, and the Linn Drum partnered with the Japanese Akai Corporation to create samplers similar to the ones created at Linn's own company, Linn Electronics. With this came the first in a series of affordable samplers, the S612, a 12 bit digital sampler module. The S612 was superseded in 1986 by the S900.
The Akai S900 (1986) was the first truly affordable digital sampler. It was 8-note polyphonic and featured 12-bit sampling with a frequency range up to 40 kHz and up to 750 kB of memory that allowed for just under 12 seconds at the best sampling rate. It could store a maximum of 32 samples in memory. The operating system was software based and allowed for upgrades that had to be booted each time the sampler was switched on.
The Akai MPC60 Digital Sampler/Drum Machine and MIDI Sequencer (1987) was the first rack mounted model released. It is also the first time a sampler with touch sensitive trigger pads was produced by AKAI, giving birth to the popular MPC series of sampler sequencers.
The Akai S950 (1988) was an improved version of the S900, with a maximum sample frequency of 48 kHz and some of the editing features of the contemporary S1000.
The Akai S1000 (1988) was possibly the most popular 16-bit 44.1 kHz stereo sampler of its time. It featured 16-voices, up to 32 MB of memory, and 24-bit internal processing, including a digital filter (18dB/octave), an LFO, and two ADSR envelope generators (for amplitude and filtering). The S1000 also offered up to 8 different loop points. Additional functions included Autolooping, Crossfade Looping, Loop in Release (which cycles through the loop as the sound decays), Loop Until Release (which cycles through the loop until the note begins its decay), Reverse and Time Stretch (version 1.3 and higher).
Other samplers released by AKAI include the S01, S20, S700, S2000, S3000, S3000XL, S5000, S6000, MPC500, MPC1000, MPC2000, MPC2000XL, MPC2500, MPC3000, MPC3000XL, MPC3000LE, MPC4000, MPC5000, Z4 and Z8.
Roland Corporation manufactured the S series. These were true samplers that provide all of the features described above, including sampling, sample editing, pitch transposition, and keyzone mapping:
More recently, Roland introduced the Groove Sampler concept. These devices are renowned for their ease of use, but lack the pitch transposition and keyzone mapping capabilities that most samplers have. This limits them to rendering loops or sound effects samples that are played back at the same pitch they were recorded. Although these machines are equipped with a wide range of built-in effects, their lack of pitch transposition and keyzone mapping diminishes their utility significantly. The Roland Groove Sampler line includes the following: