Sample
A sound or short piece of audio stored digitally in a computer, synthesizer or sampler. The word sample may refer to either a single moment in a digital audio stream (the smallest piece of data used to represent an audio signal at a given time) or a complete sound or digital audio stream made up of a collection of individual samples. For a more detailed explanation of samples, see Digital Audio Basics.

sample-and-hold
A circuit on an analog synthesizer that, when triggered (usually by a clock pulse), looks at (samples) the voltage at its input and then passes this voltage on to its output unchanged, regardless of what the input voltage does in the meantime (the hold period), until the next trigger is received. In one familiar application, the input was a noise source and the output was connected to oscillator pitch, which caused the pitch to change in a random staircase pattern. The sample-and-hold effect is often emulated by digital synthesizers through an LFO waveshape called "random."

Sampler
A hardware device or software application that uses samples as it's main method of generating it's audio output. Samplers often use a number of samples together to create realistic sounding reproductions of real sounds and musical instruments. For more details on this technique, see Wavetable Synthesis.

Sample Rate
The resolution of digital audio that determines it's sound quality. When audio is digitally recorded (digitized), it must be converted into a series of samples which can be stored in memory or on disk. The sample rate defines how many samples are recorded per second of audio input and is measured in Hz (Hertz, cycles per second) and kHz (Kilohertz, thousand cycles per second). Sample rate - Also called sampling frequency. The term describes the frequency at which analog audio material is sampled. According to the so-called "Nyquist Theorem", the highest frequency which can be accurately represented is one-half of the sampling rate - which means that at a sampling rate of 44.1 kHz, the maximum frequency would be 22 kHz, although in practice this figure is somewhat lower.

Sample rate converter
Device or algorithm that translates one sampler rate into another; this conversion always leads to some type timing problem - the quantizing goes out of whack, which degrades the audio quality.

Sampling
General term for conversion of analog to digital audio data. Tiny "samples" are taken of an analog waveshape at regular intervals, whereby each sample represents a specific numeric value. These numeric values constitute the digital audio data stream.

SCSI
Short for "Small Computer Systems Interface"; the recommended bus standard for connecting audio hard disks. Commonly used in samplers, etc.; comes in different standards (SCSI 1, 2, 3).

Scrub
To move backward and forward through an audio waveform under manual control, in order to find a precise point in the wave for editing purposes.

SDII
Sound Designer II, an audio file format. The native format of Digidesign's Sound Designer II (Macintosh) graphic audio waveform editing program.

SDK
Software development kit.

SDMI
Secure Digital Music Initiative is a forum for members of recording, consumer electronics, and computer technology industries to develop a standard framework for secure music distribution and use.

SDS
MIDI sample dump standard. SDS is used to transfer digital audio samples from one instrument to another over a MIDI cable.

Sequence
A set of music performance commands (notes and controller data) stored in a sequencer.

Sequencer
A hardware device, software application or module used to arrange (ie. sequence) timed events into some order. In digital audio and music, sequencers are used to record and arrange MIDI and/or audio events into patterns and musical compositions.

Sidebands
Frequency components outside the natural harmonic series, generally introduced to the tone by using an audio-range wave for modulation. See clangorous.

Signal-to-Noise Ratio
"Signal" refers to the useful or "pure" information found in a an audio stream or other medium, and "noise" to anything else. The ratio of these is usually expressed logarithmically, in decibels. Signal-to-Noise Ratio is sometimes abbreviated as SNR, s/n ratio and s:n ratio. A high SNR translates to a "cleaner" signal.

sine wave
A signal put out by an oscillator in which the voltage, or equivalent, rises and falls smoothly and symmetrically, following the trigonometric formula for the sine function. Subaudio sine waves are used to modulate other waveforms to produce vibrato and tremolo. Audio-range sine waves contain only the fundamental frequency, with no overtones, and thus can form the building blocks for more complex sounds
> Additive synthesis

single-step mode
A method of loading events (such as notes) into memory one event at a time. Also called step mode and step-time. Compare with real time.

Slot
General term for expansion ports on the computer's mainboard.

SmartMedia
A type of small memory card used by many portable MP3 players for storage.

SMDI
SCSI musical data interchange. A specification for sending MIDI sample dumps over the SCSI bus. See SDS.

SMP
Turtle Beach's SampleVision audio file format. Typically encountered as FILENAME.SMP.

SMPTE time code
A timing reference signal developed by the Society of Motion Picture & Television Engineers and used for synchronizing film and videotape to audio tape and software-based playback systems. Pronounced "simp-tee." See frame.

SND
Sound resource. A Macintosh audio file format.

snapshot automation
A form of mixing automation (frequently MIDI-controlled) in which the controlling device records the instantaneous settings (the snapshot) for all levels and pan pots, and recalls these settings on cue.

song position pointer (SPP)
A type of MIDI data that tells a device how many sixteenth-notes have passed since the beginning of a song. An SPP message is generally sent in conjunction with a continue message in order to start playback from the middle of a song.

sostenuto pedal
A pedal found on the grand piano and mimicked on some synthesizers, with which notes are sustained only if they are already being held on the keyboard at the moment when the pedal is pressed. Compare with sustain pedal.

Sound Card
A hardware interface that is either built into a computer's motherboard or inserted into one of the computer's internal expansion slots. Sound cards allow the computer to play digital audio and/or musical instrument sounds. Many sound cards also provide a MIDI interface.

Sound recording
Legal term for particular recording made of a song by a performer. The copyright for a sound recording is often owned by a recording company.

Space-shifting
Moving or copying content between different media, formats, or devices.

S/P-DIF
Short for "Sony/Philips Digital InterFace"; standard format for transporting digital audio data. Either an optical or a coaxial interface, depending on the type of device. The format is similar to AES/EBU, although it features unbalanced circuits and lower voltages. Nevertheless, AES/EBU and S/P-DIF coax interface can often communicate directly (depending on the type of devices involved).

spectrum of a sound
> Fourier analysis; > partial. The overtones define the harmonic spectrum of a sound

split keyboard
A single keyboard divided electronically to act as if it were two or more separate ones. The output of each note range is routed into a separate signal path in the keyboard's internal sound-producing circuitry, or transmitted over one or more separate MIDI hannels. Applications include playing a bass sound with the left hand while playing a piano sound with the right.

SPP
> song position pointer.

status byte
A MIDI byte that defines the meaning of the data bytes that follow it. MIDI status bytes always begin with a 1 (hex 8 through F), while data bytes always begin with a 0 (hex 0 through 7).

step input
In sequencing, a technique that allows you to enter notes one step at a time. (Also called step recording.) Common step values are sixteenth- and eighth-notes. After each entry, the sequencer's clock (position in the sequence) will advance one step, then stop, awaiting new input. Recording while the clock is running is called real-time input.

Streaming audio
Streaming is a method of transferring multimedia, such as audio or video in one continuous feed from sender or receiver. A streaming server parcels out a little at a time to everyone who is connected to it, and those receiving the stream can play it as it arrives without having to wait for a whole file to download. Streaming audio can be used to create a net radio station.

Sustain
The period of an envelope during which a sound's attribute (such as volume) holds at a constant level. The sustain period starts at the end of the decay period and holds until the release period is started (usually by a keyboard note release). Unlike the other periods of an envelope, the sustain period does not have a slope because it must be capable of holding indefinitely (as long as a keyboard note is pressed).

Sync
Synchronization. Two devices are said to be in sync when they are locked together with respect to time, so that the events generated by each of them will always fall into predicable time relationships.

sync track
A timing reference signal recorded onto tape. See SMPTE time code, FSK.

Syncopate
To shift the regular accent of a tone or beat by beginning on an unaccented beat and continuing through the next accented beat.

Synthesizer
A musical instrument that generates sound electronically and is designed according to certain principles developed by Robert Moog and others in the 1960s. A synthesizer is distinguished from an electronic piano or electronic organ by the fact that its sounds can be programmed by the user, and from a sampler by the fact that the sampler allows the user to make digital recordings of external sound sources.

system-common
A type of MIDI data used to control certain aspects of the operation of the entire MIDI system. System-common messages include song position pointer, song select, tune request, and end-of-system-exclusive.

system-exclusive (sys-ex)
A type of MIDI data that allows messages to be sent over a MIDI cable that will be responded to only by devices of a specific type. Sys-ex data is used most commonly for sending patch parameter data to and from an editor/librarian program.

system real-time
A type of MIDI data that is used for timing reference. Because of its timing-critical nature, a system real-time byte can be inserted into the middle of any multi-byte MIDI message. System real-time messages include MIDI clock, start, stop, continue, active sensing, and system reset.