M

MADI

Ah yes, another music industry acronym (the military has nothing on us). MADI stands for Multi-channel Audio Digital Interface and is an AES specification for digital interconnection between multitrack recorders and mixing consoles. It is an international standard (AES-10) offering 56 audio channels on a single coaxial cable or fiber-optic interface.

Mag

Short for magnetic film, a mag is where audio is temporarily stored during the post production process. A mag looks exactly like motion picture film, but with no picture on the base stock, just the usual oxide (see WFTD archive Oxide) that you find on any recording tape (the uninitiated might even look at it and figure it to be raw film stock for filming the picture). In film production the audio is transferred from analog or DAT (whatever mediums were used) to mag for the post production and editing process.

Magneto-Optical

A technology that utilizes the optical properties of a magnetized platter upon which data is stored magnetically, but read optically, using a laser. A laser heats up the magnetic material. An electromagnet then polarizes the material while it is still hot. When the magnetic surface cools, the polarity is set. Magnetic polarity affects light polarity, so a low power laser can then read the information back by determining the polarity of the reflected light.

Master

In synchronization this is the opposite of slave. In order for any two (or more) devices to sync to one another, one of them has to act as a master while others act as slaves and follow it. The master machine is, by definition, under its own control and dictates the location and timing or speed of playback. In modern applications it is often possible for a machine to be the master in one domain (such as location) while being a slave in another (such as speed). In many modern facilities all machines are driven by one master clock (speed) source and controlled by one master controller.

To master something is the act of preparing recorded material for mass duplication and is discussed in our WFTD Mastering.

Mastering

Though used (too) generically in our industry, this word can mean many subtly different things. The most common (and correct) understanding is that mastering is the process where recorded material is taken from a "master tape" and prepared for duplication in the format of the final release media. Historically this originated with transferring material from tapes to an acetate master disk, which was the first process in making phonograph records. The entire process was as much an art as a science, and as production quality and technology advanced, many practices were developed that helped make better and better sounding records. This advancement included many potential processes of the audio signal such as equalization, compression, limiting, normalization, widening the stereo image, editing fades, and just putting the songs in the correct order. They started out as simple tweaks that had to be done to make audio play correctly on vinyl records, but producers learned that a good mastering engineer could be the difference in how an album ended up sounding as a whole. A well mastered record was better and more consistent in terms of levels and tone quality, which became more and more important as radio airplay and home hi-fi systems became more prevalent in our society.

Nowadays, with the convenience, quality, and affordability of digital audio equipment, many of these steps are done in the recording studio (home or otherwise) where the material was recorded. A significant percentage of the equipment sold at Sweetwater Sound is for this purpose and is being purchased by beginners and pros alike. Still, however, the last few steps of the mastering process, which is very different for CD's than it was for LP's (see WFTD archive LP), are done after the material leaves the studio. Sometimes an actual mastering house is used, and other times the "mastered" material is sent directly to a duplication facility where they can also do the final few steps. The lines between how much of it are done in the studio, versus a mastering house, versus the duplication house are very blurry at this point.

More in depth info on mastering can be found at the following Web sites:

• http://www.digido.com/
• http://www.audiodirectory.demon.nl/mastering.html
• http://www.essrl.wustl.edu:80/~adl/mastering/
• http://www.drtmastering.com/biz/drt/faq2.htm#whatis

Maximum SPL (Sound Pressure Level)

A common specification for microphones, max SPL indicates the highest sound pressure level a mic's electronics can handle before the onset of distortion. Normally, this spec is referenced to 0.5% distortion at 1 kHz. Keep in mind that the presence of an attenuator switch on the mic may allow an increase in the volume level the mic can absorb before distorting.

Obviously, this is an important spec for many applications - if the mic is going to spend its life in front of a screaming Marshall stack, or in a kick drum, it must be able to adequately deal with the volumes it will be seeing...

MDM

Abbreviation for Modular Digital Multitrack. It pertains to any digital multitrack tape machine that is designed to work in conjunction with other like machines such that together they effectively build a "machine" with more tracks and/or capabilities. The Alesis ADAT and Tascam DA series machines are the most noteworthy examples, but others have been built by Fostex, Sony, Panasonic, and Studer. Compatible machines of different brands can be "linked" together under the modular environment, but otherwise they can only be synchronized together much the same way any dissimilar recorders traditionally have been.

Metal Particle Tape

Sometimes just referred to as metal tape, a type of magnetic tape that uses microscopic particles of iron rather than iron oxide as the magnetic medium. Metal tape is capable of much better performance than oxide tape, especially at high frequencies, but it requires a different equalization and bias. The improvement is most pronounced at low tape speeds, which is why it has been such a popular formulation for cassette tapes. The disadvantage of metal particle tapes is that they tend to be a little less flexible and more abrasive to the heads, causing both more shedding and head wear. Newer machines employ tape heads specifically designed to be used with this tape.

Mic Level

The level (or voltage) of signal generated by a microphone. Typically around 2 millivolts. Compare this with the two normal line levels (1.23 volts and .316 volts), and it becomes apparent just how much amplification is going on in a microphone preamp, and why it is essential that preamps be of as high quality as possible!

Microphonic

Sometimes components in an audio device become or are sensitive to vibration, and convert that vibration into audio signals. Tubes are a common culprit. When tapped, a microphonic tube will output noise. Other components can also become microphonic, although solid-state components are less susceptible. Audio cables can also become microphonic, adding noise to a signal when moved, or vibrated.

MIDI

Today's word may seem a bit basic to many of you, but we did have a request for it: MIDI Ü An acronym for Musical Instrument Digital Interface. MIDI was developed back in the early 1980's as a standardized protocol for communication between electronic musical instruments and peripherals. It allows MIDI devices to transmit and receive almost every aspect of a musical performance. Today MIDI is used in all sorts of applications, including synchronization, sequencing, lighting control, automation systems, more. There are many different types of MIDI messages that are used in MIDI for various applications. A typical MIDI connection is made with a MIDI cable, which has a 5-pin DIN type connector of which only three pins are used (except in some special applications).

MIDI Clock

A MIDI timing reference signal used to synchronize pieces of equipment together. MIDI clock runs at a rate of 24 ppqn (pulses per quarter note). This means that the actual speed of the MIDI clock varies with the tempo of the clock generator (as contrasted with time code, which runs at a constant rate). Also note that MIDI clock does not carry any location information - the receiving device does not know what measure or beat it should be playing at any given time, just how fast it should be going.

MIDI Implementation Chart

MIDI implementation refers to the specific MIDI messages and signals a piece of gear can recognize; a MIDI implementation chart is therefore a listing of the messages a particular device can transmit and recognize. This can be very useful when attempting to determine if a device can send and/or receive various types of channel or system messages. Normally found in the back of the device's manual, its MIDI implementation chart will consist of a list of available MIDI messages, whether the device incorporates those messages, and any special notes or limitations on how it deals with those messages. For example, the chart will list the MIDI channels and modes, note numbers, and continuous controllers the device can respond to. Support for aftertouch, velocity, pitch bend (often with bit resolution), and program change will be indicated. Also listed will be recognition of system exclusive, system real time (clock commands), system common (song position, song select, etc.) and aux messages (local on/off, all notes off, active sensing, and so on).

MIDI Machine Control (MMC)

A part of the MIDI spec that allows MIDI devices to control hardware devices, MIDI Machine Control is commonly used to send transport control messages to hardware recorders. Play, Stop, and Locate are examples of MMC messages. Note that MMC does not include synchronization information, although MIDI sync info could also be sent to/from the device that MMC is addressing. MMC allows you to centralize control of your studio from a MIDI source (often a sequencer). A common scenario: Pressing play on a MIDI seqencer sends an MMC play message to a connected multitrack recorder, which begins playing. As the deck plays, it generates MIDI Time Code (MTC) which the sequencer then synchronizes to (chases). When "stop" is pressed on the sequencer, the deck also stops, and ceases to send out MTC. When MTC stops, the sequencer stops chasing. Locating to a point within the sequence will cause the deck to fast forward or rewind to the corresponding location on tape.

MIDI Mode

One of several ways in which a device can respond to incoming MIDI information. There are two parts to each mode, one defining whether it is monophonic or polyphonic, and the other determining if it is multitimbral or not. Four modes are included in the MIDI spec, and two others, Multi Mode and Mono Mode (for MIDI guitar) were developed later.

1. Omni On/Poly - Device responds to MIDI data regardless of channel, and is polyphonic. (See WFTD "Polyphonic")
   
2. Omni On/Mono - Device responds to MIDI data regardless of channel, and is monophonic. This mode is rarely, if ever, used.
   
3. Omni Off/Poly - Device responds to MIDI data only on one particular channel, and is polyphonic. This is the normal mode for most keyboards that are not functioning multitimbrally.
   
4. Omni Off/Mono - Device responds to MIDI data only on one particular channel, and is monophonic.

Multi Mode - Used by many devices for multitimbral operation. An expanded version of Mode 3, Multi Mode allows the device to respond to several independent MIDI channels at once, with each being polyphonic. (See also WFTD "Multitimbral")

Mono Mode - Used for MIDI guitar applications, Mono Mode is an expanded version of Mode 4, allowing for six Omni Off/Monophonic channels to be used at once, one for each string of the controller. This allows for better tracking, independent pitch bend per channel, and a separate sound or patch assignment per channel.

MIDI Time Code (MTC)

A form of time code representing real time in Hours: Minutes: Seconds: Frames: Subframes, and transmitted over MIDI.

MTC can also be described as a way of sending SMPTE time code over MIDI cables. Like all forms of time code, MTC is designed to allow various pieces (in this case MIDI-equipped) of equipment to synchronize together.

Mono

Short for monaural, mono means only one audio channel, as opposed to stereo, which means two (usually a left and a right), and quad, which means four.

Modulation

Literally, modulation is change. In music technology, the term normally applies to a control signal being used to change some aspect or parameter of another signal. For example, a regularly repeating sine waveform might be added to a pitched note to produce vibrato, or a control voltage might be used to change (modulate) a filter cutoff frequency. A whole category of synthesis (and radio broadcasting), FM (frequency modulation), is based around using the frequency of one signal (the modulator) to change the frequency of another audible signal (the carrier). Likewise, AM radio works because of amplitude modulation, or using one signal's volume to modulate another signal.

Modulation Noise

Noise which is present only in company with a signal. In analog recorders the recording process has a certain "granularity" due to the fact that the magnetic characteristics of the tape are not completely uniform which causes an irregularity in the recorded signal that sounds like noise. In digital audio systems there is also an "uncertainty" in the level of the signal because of quantization (see WFTD archive Quantization Error) in the A/D converter (see WFTD A/D converter). This uncertainty sounds like added noise and is not present if the signal is not present.

MPEG

An acronym for Motion Picture Experts Group. They manage the standards for encoding audio and video in digitally compressed forms. With the development of so many new (yet limited) distribution channels for audio and video data the importance of standardized compression schemes is at an all time high. There are several different types of MPEG compression in use today, and within each of those there are different levels of compression. Some compress more than others do. The type and severity of MPEG compression specifically used will depend largely upon the intended distribution channel for the data (DVD, CD-ROM, Internet, etc.).

MPU-401

A MIDI interface developed by Roland in the early 1980's for PC compatible computers. This very early MIDI interface became the de facto standard for all PC interfaces. Other interfaces that came out in years to follow began to be "MPU-401 compatible." Before long the only accepted interfaces had to be MPU-401 compatible and the core elements of the standard lives on (though unspoken now) to this day.

MSB

Contrary to LSB, MSB is an abbreviation for Most Significant Bit. This is the bit of any digital word that has the most impact on its mathematical value. This bit is at the opposite end of the word (usually the left end) from the LSB.

MTBF

Abbreviation for Mean Time Between Failure. MTBF Is a statistical term relating to reliability as expressed in power on hours (p.o.h.) and is often a specification associated with hard drive mechanisms. It was originally developed for the military and can be calculated several different ways, yielding substantially different results. It is common to see MTBF ratings between 300,000 and 1,000,000 hours for hard disk drive mechanisms, which might lead you to conclude that the specification promises between 30 and 100 years of continuous operation. This is not the case! The specification is based on a large (statistically significant) number of drives running continuously at a test site with data extrapolated according to various known statistical models to yield the results. Based on the observed error rate over a few weeks or months, the MTBF is estimated and not representative of how long your drive, or any individual product, is likely to last, nor is it a warranty. It is representative of the relative reliability of a family of products. A higher MTBF merely suggests a more reliable and robust family of mechanisms (depending upon the consistency of the statistical models used).

Mult

Short for "multiple", mult refers to the parallel wiring of the jacks in a patchbay. Several jacks are wired together so that input to one of them will feed all the others; a mult is a passive splitter or "y" connection. Mult is also used as a verb by audio engineers, as in "We'll mult the output of your Casio CZ-101 so that it feeds all 108 inputs on your Euphonix console..."

Multisession

A CD-R is multisession if information can be added to a disc that has already been written to once (note that data is being added to the "end" of the CD, old data is not being erased, rewritten, or removed). This is also referred to as "Orange Book" standard. This is a fairly common format when CD-Rs are used for CD-ROM archival, and for Kodak format Photo CDs. In the audio world, many stand-alone CD recorders initially write CDs as multisession discs. Then when all the audio required has been written to the disc, it is "fixed up", or has a table of contents add. This essentially converts it to a standard Red Book audio CD, readable in regular CD players.

Multitimbral

A synthesizer or sampler is multitimbral if it is capable of producing more than one type of sound or timbre (pronounced tam bur) at a time. Usually this is described as the number of "parts" a unit can play at once. For example, a Kurzweil K2500 is 16-part multitimbral, meaning it can produce 16 different sounds at once (a sound being defined as a single patch or preset; part one might be piano, part two strings, part three trombone, part four flute, and so on. Generally these parts are assigned to different MIDI channels for independent control). This is distinct from the amount of polyphony, or number of actual notes the unit can simultaneously generate. Using the K2500 example again, a 16-part multitimbral K2500 can produce up to 48 notes of polyphony distributed dynamically across those 16 multitimbral parts.