tags: music sampling electroacoustic composition synthesis
Sampling (composition)
History
Broadly, there are two categories of [electroacoustic] [composition]:
- [synthesis] (generated audio)
- sampling (recorded audio)
Composed manipulations of recorded sound via variable-speed phonographs date back to 1920s (D. Milhaud, E. Toch, P. Hindemith).
Magnetic tape (1930s) enabled more fluid manipulation of recorded audio
- Imaginary Landscape No. 1, John Cage
Musique concrète was an early form of sampling, primarily concerned with tape splicing, manipulation, and looping.
- objet sonore
Early Sampling Instruments
Operating principles include:
- sound encoding on optical discs (photoelectric effect)
- sound recording on magnetic tape
In general, all these instruments work to achieve the same thing; creative expression through manipulation of recorded audio.
- [Light Tone Organ] (Licht-Tone Organ) - Edwin Welte, Germany, ca. 1936
- [Phonogène] - [Pierre Schaeffer], Paris, ca. 1950s
- [Special Purpose Tape Recorder] - Hugh Le Caine, 1955
- [Mellotron] - Birmingham, England, 1963
Digital Sampling Instruments
- [Fairlight CMI] (1979)
- [E-Mu Emulator I] (1981)
Sampling techniques were greatly enhanced by [midi] (1983). Numerous other sampling instruments were introduced by Akai, Roland, Kurzweil, Ensoniq.
Techniques and Terminology
keymapping: assigning samples to [midi] note numbers
- sometimes multiple samples per note, or one sample for multiple notes
- key aspect of designing samplers - how do we let the user choose which keys are mapped to which samples?
root key: the [midi] note number that plays back a sample at its original speed/pitch
- usually you want to map pitched samples to the matching key on the keyboard (ex. playing middle C on the keyboard should result in a middle C)
- but can also move the root key and exaggerate its position for interesting effects
key zone/key range: a contiguous region of [midi] note numbers that plays back a single sample, usually transposing pitch based on note number
- can be every keynum (0-127), but not always
- ex. a virtual cello instrument's key zone could be mapped to only the physical acoustic range of a cello
- can also have many contiguous zones
- large key zones can create problems at extremes: high/low numbers can result in extremely unrealistic sounds
multisampling: recording multiple pitches across an instrument's range and keymappping to smaller key zones
- ex. if you have a library of violin samples, but not every chromatic pitch, you can map multiple keys to each violin sample to cover every chromatic pitch
- usually sounds okay to transpose a sample only a few steps
- used to reduce the number of samples (and therefore storage used)
- helps alleviate problems with few samples/large zones
chromatic multisampling: creating a separate audio sample for each chromatic pitch on an instrument, and using 1:1 keymapping
- greater sense of realism, but greater memory storage required
velocity switching: using [midi] velocity values to select from multiple samples assigned to the same [midi] note number
- ex. to accurately model a piano, different samples are needed for playing fortissimo vs. pianissimo
- useful in simulating timbral differences encountered when playing an acoustic instrument at different intensities
keyswitching: using a [midi] note number outside an instrument's typical range to switch between banks of samples
- ex. C2 activates a bank of bowed (arco) violin samples. C#2 activates a bank of plucked (pizz) violin samples
looping: see: [looping]
sample patch: a pre-configured sampler instrument which has undergone many of the previously mentioned techniques (multisampling, keymapping, velocity switching, keyswitching, predetermined loop points)
sample library: a software package containing several pre-configured sample patches
downsampling: when an audio sample is transposed (pitch-shifted) upwards, some sampler [algorithm]s will skip a number of sample values in the audio file (see: [sampling in signal processing]), in proportion to the amount of pitch-shift specified. Also called decimation.
- this process of upward transposition can cause [aliasing], which prompts the use of [anti-aliasing filters]