L

Land

1. To touch down after flight.
2. To arrive, as in after a 14 hour drive from Fort Wayne to New York City in a loaded truck destined for the AES show.
3. The opposite of sea; the ground, earth, etc.
4. The area between the grooves (actually "groove" is more accurate) of a vinyl record (remember those?).
5. The area between the pits on a compact disc.

Latency

You'll see this term used in a variety of contexts, but it means essentially the same thing: Latency is the amount of time it takes for a device to respond to a command. In a MIDI instrument, it might be the time between a "note on" message being sent, to when that note actually sounds (might be different figures for single notes, chords, or multitimbral operation). In a hard drive, there is rotational latency; in a hard disk recording system, there is latency in getting all the tracks to sound, and so on.

Lavalier

A lavalier (a.k.a. Lapel Mic) is a small microphone designed to be worn on clothing or to hang around one's neck. They are used in applications where a large hand held microphone would either be too cumbersome or unsightly, or both. They are typically made with an extreme low frequency rolloff to reduce rumble and noise from moving against clothing.

Layback

What your inSync editor wishes he was doing this Super Bowl Sunday instead of walking his legs off at the NAMM show. In the domain of audio/video production layback is the process of laying audio back in to video for the final video product. During video projects it is common for the audio and video to be edited separately (sometimes in separate facilities in different states or countries). Once the video and its audio are finalized they are combined together. This process is called layback and has historically been done on layback machines that are designed for this purpose.

Leader Tape

Used in analog tape recording, a non magnetic plastic or special paper tape that is spliced onto magnetic tape in between musical selections and at the beginning and end of the magnetic tape. Leader protects the magnetic tape, identifies the beginning and end of selections, and provides a near dead silent space between selections (even blank magnetic tape has some hiss).

LED

Abbreviation for Light Emitting Diode. It is not an acronym. You do not pronounce it as "lead." It is pronounced EL - EE - DEE. An LED is an electronic component that glows when current passes through it. LED's are found in all sorts of electronic equipment these days from watches to laser disc players (in fact the laser that reads the disc is usually an LED). The lights that glow on top of your keyboard are almost surely LED's. The numerical readout and meters on your DAT machine are almost surely LED's. LED's do not always produce visible light. Infrared LED's are used in wireless remote control devices as well as things like wireless headphone systems.

LEDE - Live End, Dead End

LEDE is a trademarked term for a particular acoustic design. In an LEDE studio, the area around the monitors is deadened, or made absorbent acoustically. The remainder of the room (behind the listener) is made "live" or reflective. The main principle is that the arrival of reflections at the console is in a specific order: 1. direct sound from the monitors; 2. First studio reflection (from the recording room, through the mics and monitors); 3. First control room reflection (off the back wall, assuming it is 10 feet or so behind the engineer). The idea is that by staggering these arrivals, the control room reflections don't interfere with monitoring recorded studio acoustics.

Leveler

A leveler is a device which uses an audio gain circuit to increase or decrease the level of audio passing through it based on parameters set by the user. The purpose is not specifically to reduce the dynamic range of a signal like in a compressor or limiter (though that is often what happens), but to simply have an audio signal stay at roughly the same volume for an extended period of time. Most levelers are not sensitive to peaks of a short duration, but affect very gradual changes to audio level as input levels gradually change over time. Sometimes levelers are referred to as automatic gain controls (AGC). A high quality leveler will work far better and more transparently than the typical AGC control you might have used that was built into an audio or video tape recorder.

LFE

Abbreviation for Low Frequency Effects, a term used in surround sound mixing. Low-frequency effects are mixed to a separate so-called LFE channel in modern movie sound production. The LFE channel carries non-essential effects enhancement - such as the low-frequency component of an explosion - often at higher levels than the other channels. The idea behind a separate LFE channel is to provide the extra low-frequency headroom needed to put low-frequency signal components on equal psychoacoustic footing with midrange signal components which require less energy for the same perceived loudness.

Librarian

In music production a librarian is software whose function is to organize and store program information for MIDI instruments and processors. Librarians can store thousands of different sets of patch data for each device in a given system. In other words, they store and organize the actual computer data the device uses to set itself up to make the various sounds it can make Ü the parameter data if you will. They sometimes employ databases so patches may be searched on key words or attributes of the sound. They can upload or download the data to and from instruments connected via MIDI by using strings of system exclusive commands. This makes it very easy to change the entire contents of program memory of a given device for each session or job needing to be done.

Light Pipe

Basically this is a $3 phrase that means optical cable. The phrase was more or less coined by Alesis to help make the distinction between their proprietary 8-channel optical network used in ADAT products and standard optical connectors used on CD players and other consumer gear. When one speaks of a "light pipe" connection it is usually assumed that it is in reference to one that will transfer data as defined by the ADAT protocol, which is an eight-channel format as opposed to the two-channel format of most consumer products.

Limiter

A limiter is a dynamics processor very similar to a compressor (see inSync WFTD 10/13). In fact, many compressors are capable of acting as limiters when set up properly. The primary difference is the ratio used in reducing gain. In a limiter, this ratio is set up to be as close to infinity:1 as possible (no matter how much the input signal changes, the output level should remain pretty much constant). The idea is that a limiter establishes a maximum gain setting, and prevents signals from getting any louder than that setting.

Like compressors, limiters are used for a variety of applications. A few: Maximizing signal levels while preventing distortion when using digital recorders, preventing overload in a signal chain, setting a maximum volume level to protect users of in-ear monitors, protecting speakers and amplifiers from clipping, and so on. Any time you want to establish a maximum gain setting and prevent signals from passing it, a limiter is your tool of choice!

Linear Interpolation

Of or relating to a line. In audio, linearity is a very important concern. A linear system is one whose function is even or, if it deviates, does so in a steady fashion. Logarithmic or exponential deviations are, by definition, non-linear. We've all heard the term "flat" used to describe frequency response. Flat is considered good. It is also linear. On a graph it looks like a straight line instead of a wavy line. A wavy line would imply non-linear frequency response, or one that is uneven. This is generally not considered a "good" quality in audio equipment, though there are plenty of exceptions. Linear does not necessarily mean horizontal though. A linear system can also be one that gradually increases or decreases in a steady fashion. Such is the output of a crossover or some EQ filters: a 12 dB per octave roll-off (which is common) is a linear decrease in level by 12 dB per octave. The actual sound level increase produced by a typical (audio taper) fader on a mixer is, however, non-linear. It is designed as a logarithmic taper to more closely match the non-linear sensitivity of human hearing. We hear the change, however, as linear in volume over their range (if they are good ones). Basically, if whatever we are interested in can be plotted on a graph as a line that doesn't curve it is considered linear.

Linear Interpolation

In digital recording, linear interpolation (also known as averaging) is a method of error concealment. This method looks at the values before and after a bad digital word (digital profanity?) and replaces the error with an average of those values. This method works acceptably well provided there is only a single error; multiple consecutive errors become problematic when using linear interpolation.

Linearity

In an analog to digital, or digital to analog converter, linearity refers to the ability of the converter to record or reproduce various signals, particularly low level signals, at the correct amplitude. For example, when a bit changes from 0 to 1 in a D/A converter, there must be a corresponding change in the analog signal output. Any non-linearity results in audio signal distortion. For a variety of reasons, it is impossible for a converter to be exactly linear, but high-quality units can come very close. In addition to poor design or quality, non-linearity can result from bit weighting errors, thermal or physical stress, aging, temperature variations, and other factors.

Line Input

On mixing boards this is an input to a channel that is specifically designed for line level signals. Unlike the XLR microphone input, which is designed for low level mic signals, line inputs are usually 1/4 inch connectors, and are quite often unbalanced, though this will vary depending on the mixer. Line level signals are usually much higher than typical mic level signal and do not need as much amplification to be dealt with by the rest of the mixer. As such, on some mixers, the line inputs actually bypass the microphone preamp stage providing for a pure signal path into the board. Regardless of this, however, line inputs are always capable of handling higher level signals and high impedance signals better than the XLR mic input.

Line Level

Literally, the average voltage of an electronic audio signal. While technically any voltage over 25 millivolts RMS is considered line level, in the modern audio world we narrow the scope a bit to the two line level references in use today: Balanced "pro" gear runs at around +4 dBm (1.23 volts), while unbalanced "semi-pro" gear operates at approximately .316 volts (-10 dBV). "Pro" and "semi-pro" may be almost meaningless terms anymore, but the two operating levels must still be dealt with. The important thing is to match the levels of the gear you are using so that -10 equipment isn't directly feeding +4 equipment, and vice versa. If you use gear of both levels, there are various level matching devices on the market to properly interface the items.

Load

In electrical terms a load is something that dissipates power and does some work. The work done may take many forms, including generating heat as almost always happens as a side effect of work being done. Without a load no power can be transferred. A speaker is the load for a power amp. In order for current flow to occur a complete circuit must exist. In order for the circuit not to be a short-circuit (a decidedly bad thing) a load must be present to the power the amp. The power amp drives power through the circuit by way of increasing the voltage at its outputs and as a result the load (speaker) draws current and does work. In this case two major forms of work occur: The speaker moves and generates sound, and heat is produced. Any device you plug into an electrical outlet can be considered a load (toaster, light bulb, etc). Plug in too many devices drawing too much current and you will "load down" the power delivery system (another bad thing). In order to protect against this power delivery systems have fuses and circuit breakers to break the circuit when current flow gets too high. Many power amps employ current limiting devices in their output stages to limit current flow without interrupting the audio. It's sort of a self regulating protection system (back in the old days the amp just blew up). An important thing to understand is that a load will DRAW from an available pool of power all of the current it needs to operate at the given voltage. This is somewhat simplified, but in principle remains fundamentally true for all electrical systems. A speaker's impedance rating is an indication of what kind of load it presents to an amplifier. An appliance's current or amperage rating is exactly the load it will place on the electrical system. The reason a speaker cannot be rated in exact terms of current usage is because the voltage and frequencies presented to it constantly change. Impedance is a way of approximating a speaker's resistance to a varying voltage and frequency signal.

Also related to us is acoustical loading. The efficiency of a loudspeaker depends to some extent on the acoustic load placed on it by the way it couples to a cabinet and the surrounding structures. A speaker placed in the throat of a horn, for example, will see a higher acoustic impedance than a speaker placed in a free space.

Local Control

A parameter found in many MIDI keyboards. Local control determines whether a MIDI device responds to its own keyboard and controllers (local control on) or only to incoming MIDI messages (local control off).

Lock Up

A phrase used to indicate two things operating in sync with one another. Synced equipment can be said to be locked up. Though the phrase is often used without discrimination there is actually a distinction between equipment that is truly "locked" and equipment that is merely synchronized. For example, it is impossible for two analog tape machines to be truly locked. Locking implies that clocks are tied together and running as one, as is often the case in digital audio. Synchronization implies that changes in a master device will (eventually) be reflected in a slave device in order to keep it in sync. It's a subtle but sometimes important difference.

Lock Up also refers to an unfortunate state CPU based equipment gets into from time to time. In this context locking up means "to crash" or "to freeze" where the device in question is no longer responsive and must be rebooted.

Long Throw

A down field pass (usually of more than 20 yards) in football. In music performance, anything thrown from the audience that makes it on to the stage at a concert (i.e. Beer bottles, shoes, or women's underwear). In music equipment, long throw has references for loudspeakers and loudspeaker enclosures.

In a loudspeaker long throw refers to the ability of a speaker cone to travel long distances in and out without encountering nonlinearities in its response. In speaker enclosures (high frequency horns especially) long throw refers to a shape that "focuses" the sound energy in a tighter pattern so that it will travel farther in a coherent fashion. Some horns are designed to spread the energy into a wide pattern for coverage while others are designed to be "long throw." Usually a long throw horn is recognizable by the long "throat" between the driver and the horn opening. Long throw speaker cabinets usually have the speakers recessed into some kind of horn like shape as well.

Loop

Common sense probably gives one an idea what a loop is. In audio it is a sound that continually repeats itself over and over again. It is called a loop because back in the "old days" tapes were used. One could cut a section of tape out with a sound or passage and connect the end of it back to the beginning and form a physical loop. The audio would repeatedly play over and over in a tape machine. This innovation was used by companies who manufactured tape based looping delay or echo units such as the Echoplex and Roland Space Echo. The 8-track tapes of the 1970's were an endless loop system. They never had to be rewound. In digital keyboards "looping" became a standard way to allow the sustained part of a sound to decay without having to have an actual (memory hungry) recording of the entire decay of the sound. Most sustained musical sounds fall into a relatively static state after a second or two. At that point it is possible to loop the static portion of the sound and have it play over and over while a VCA (or pick the name of this function in your synth) cause it to fade away simulating the actual decay of the instrument. "Looping" is the process of finding good loop points in sounds so they can be made to take on desired characteristics while looped. Often it is desired to loop sample so it accurately recreates some instrument, which can be quite difficult. In the 1980's and 90's looping became an art form and quite often loops would make or break sounds used in digital instruments. In recent years audio loops of entire musical passages have become very popular. A looped rhythm section, for example, can be a great foundation for another tune or arrangement.

Low Frequency Oscillator (LFO)

An oscillator is an electronic circuit which produces periodic or regularly repeating waveforms; i.e. sine, square, sawtooth, or triangle waves. An LFO is an oscillator producing these waveforms at a very low frequency or pitch. These slowly vibrating, generally subsonic waves (0 - 20 Hz or so) are often used to modulate or change a parameter in a synth, sampler, or effects processor. One common application is modulating the pitch of an audio oscillator with an LFO; this results in vibrato. If the volume of an audio oscillator is modulated with an LFO, the result is tremolo. Just about any time you see a "modulation" control on a device, it is controlling an LFO, and being used to periodically change some parameter.

Low Note Priority

A subset of MIDI Mode #4 (see WFTD archive MIDI Mode) that determines which notes sounds if many are played on a synthesizer set up for MIDI mode #4 (i.e. to play monophonically). When more than one note is played on a monophonic synthesizer, only the lowest note will sound. The lowest note has priority over the other notes. In some synthesizers this priority can be changed to highest note played or to last note played, but many default to Low Note Priority.

Lowpass Filter

A filter specifically designed to remove frequencies above the cutoff frequency, and allow those below to pass unprocessed is called a lowpass filter. The effect of a lowpass filter is to turn down high frequencies. Common examples include the "treble" controls on many lower end radios and stereos, the passive "tone" controls often found on electric guitars and basses, hi-cut filters on consoles, and of course, this type of filter is found on many synthesizers.

LSB

Abbreviation for Least Significant Bit. The least significant bit of any digital word is the one that, when changed, has the least affect on the overall mathematical value of the word. When looking at a word as a binary series of one's and zero's (1001001) it is the right most digit, or bit.

LSB also stands for Lower Side Band, which is a term denoting the sideband produced by the difference frequencies when one signal is modulated by another as in FM synthesis or broadcast transmissions.

The result of one signal or waveform being modulated by another (or others). When a signal is either frequency modulated (FM) or amplitude modulated (AM) by another signal sum and difference frequencies are produced that appear with the signal. These are known as sidebands. The Upper Sidebands (USB), which are the result of adding the signals together, and Lower Sidebands (LSB), which are the result of subtracting them. Sidebands are a phenomenon that occur in FM and AM radio stations, but they are most relevant to us because they are a phenomenon that occurs in FM Synthesis. They are a big part of what gives FM synthesizers their unique sound.

LTC

Abbreviation for Linear Time Code. Some references refer to it as Longitudinal Time Code to make a clear distinction between it and VITC (Vertical Interval Time Code), which is normally used in video. LTC is Time Code that is written sequentially along the length of a piece of analog tape or on the linear audio track on some video tapes. It is the most common method of deploying time code. Nowadays LTC can usually be generated from subcode or other proprietary information on digital tape or hard disk units, but it is still referred to as LTC because it appears as standard linear time code at the output of those devices.