Sampler (musical instrument)

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An AKAI MPC2000 sampler
An AKAI MPC2000 sampler

A sampler is an electronic music 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.

Most samplers have polyphonic capabilities: they are able to play more than one note at the same time. Many are also multitimbral: they can play back different sounds at the same time.


Contents

[edit] Sampler Structure

[edit] Interface

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.

Fig. 1: An example of how multiple samples can be arranged across a keyboard range. In this example, four different recordings of a violin are distributed across 12 notes. Each sample will play back at three different pitch values
Fig. 1: An example of how multiple samples can be arranged across a keyboard range. In this example, four different recordings of a violin are distributed across 12 notes. Each sample will play back at three different pitch values

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.

[edit] Hierarchy

A sampler is organized into a hierarchy of progressively more complicated data structures.

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 effects 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.

[edit] Parameters

Samplers can be classified in terms of a variety of parameter capabilities.

  • Polyphony: How many voices can play simultaneously
  • Sample Space: How much memory is available to load samples
  • Channels: How many different MIDI channels are available for different instruments
  • Bit depth: how much sample resolution can be supported
  • Outputs: How many discrete audio outputs are available.

[edit] Historical Overview

The emergence of the digital sampler made sampling far more practical, and as samplers added progressively more digital processing to their recorded sounds, they began to merge into the mainstream of modern digital synthesizers. The first digital sampling synthesiser was the Computer Music Melodian which was first available in 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.

Modern digital samplers use mostly digital technology to process the samples into interesting sounds. 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.

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 O1W and the later Korg Triton and Korg Trinity series, Yamaha's SY series and the Kawai K series of instruments.

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.

Samplers, together with traditional Foley artists, are the mainstay of modern sound effects production.

[edit] Examples of digital samplers

[edit] Computer Music Melodian

Computer Music Inc. was started in New Jersey USA in 1972 by Harry Mendell and Dan Coren. The company was established to develop and market musical instruments based on computer software.

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.

[edit] Fairlight Instruments

Fairlight Instruments was started in Sydney Australia in 1975 by Peter Vogel and Kim Ryrie. The company was originally established as a manufacturer and retailer of video special effects equipment.

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 8-bits at a rate of 10 kHz and was comprised of two 8-bit Motorola 6800 processors, which were later upgraded to the more powerful 16/32-bit Motorola 68000 chips. 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.

In 1982, Fairlight released the Series II which doubled the sampling rate to 16 kHz. The Series IIx was released in 1983 and was the first to feature basic MIDI functionality. 1985 saw the release of the Series III which upped the sampling resolution to 16-bits. SMPTE was also added in this final version. Notable users of the Fairlight CMI include Peter Gabriel, Trevor Horn, Art of Noise, Yello, Pet Shop Boys, Jean Michel Jarre,and Kate Bush.

[edit] E-mu Systems

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-bit sampling, up to 1 MB of sample memory, 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.

[edit] Akai

Akai entered the electronic musical instrument world in 1984 with the first in a series of affordable samplers the S612, an 8bit digital sampler module. The S612 was superseded in 1986 by the 12 bit 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 non rack mounted model released. It is also the first time a sampler with touch sensitive trigger pads was produced by AKAI.

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 MPC500,MPC1000, MPC2000, MPC2000XL, MPC3000, MPC3000XL, MPC3000LE,MPC4000 and the MPC60

[edit] Roland

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:

  • Roland S-10
  • Roland S-50
  • Roland S-330
  • Roland S-550
  • Roland S-760
  • Roland S-770

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:

[edit] Other Manufacturers

The Yamaha PSR-295, one of Yamaha's popular entry-level keyboard samplers
The Yamaha PSR-295, one of Yamaha's popular entry-level keyboard samplers

[edit] Software Based Samplers

Recently, the incredible increases in computer speed and power have made it possible to develop software applications that can produce the same level of performance and capability as hardware-based units. Unfortunately, most vendors of software based samplers have taken serious shortcuts that limit the potential of these products. For example, most "soft-samplers" lack sample editing, sample recording capability, top-flight DSP effects, and resampling. While these products are significantly easier to use than typical hardware samplers, their ease of use stems at least partially from the fact that their capabilities are nowhere close to those provided by real samplers. The "soft-sampler" term itself is really a misnomer, because in only a few cases do these products actually sample. Soundbank players would be a more accurate and less misleading term for most of these products. For people that require the creative possibilities and workflow only a true sampler can provide, there are fortunately some real software samplers available. These products record samples, and provide sample editing and comprehensive DSP effects, as well as the other functions expected from a sampler:


A list of popular soundbank players follows:

  • Digidesign Samplecell - Hybrid system that relied on a dedicated card (originally NuBus, then PCI), along with software.

[edit] See also

[edit] External links

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