Roland MT-32
Encyclopedia
The Roland MT-32 Multi-Timbre Sound Module is a MIDI synthesizer
Synthesizer
A synthesizer is an electronic instrument capable of producing sounds by generating electrical signals of different frequencies. These electrical signals are played through a loudspeaker or set of headphones...

 module first released in 1987 by Roland Corporation
Roland Corporation
is a Japanese manufacturer of electronic musical instruments, electronic equipment and software. It was founded by Ikutaro Kakehashi in Osaka on April 18, 1972, with ¥33 million in capital. In 2005 Roland's headquarters relocated to Hamamatsu in Shizuoka Prefecture. Today it has factories in Japan,...

. Along with its compatible modules, it established an early de-facto standard in computer music and was the first product in Roland's ミュージくん (myūjikun) line of Desktop Music System (DTM) packages in Japan.

Within Roland's family of LA synthesizers, the multitimbral
Multitimbral
Monotimbral is usually used in reference to electronic synthesisers which can produce a single timbre at a given pitch upon pressing a single or multiple keys .An electronic musical instrument may be...

 MT-32 series constitutes the budget prosumer
Prosumer
Prosumer is a portmanteau formed by contracting either the word professional or less often, producer with the word consumer. For example, a prosumer grade digital camera is a "cross" between consumer grade and professional grade...

 line for computer music at home, the multitimbral D-10/D-20/D-110 models the professional line for general studio use, and the high-end monotimbral D-50/D-550 models for sophisticated multi-track studio work.

Features

Like the Roland D-50
Roland D-50
The Roland D-50 is a polyphonic 61-key synthesizer produced by Roland. It was released in 1987. Its features include Linear Arithmetic synthesis, on-board effects, a joystick for data manipulation, and an analog synthesis-styled layout design. The external Roland PG-1000 Programmer could also be...

 Linear Synthesizer, it uses Linear Arithmetic synthesis
Linear Arithmetic synthesis
Linear Arithmetic synthesis, or LA synthesis, is a term that was invented by the Roland Corporation when they released their ground-breaking D-50 synthesizer in 1987.- Overview :...

, a form of sample-based synthesis
Sample-based synthesis
Sample-based synthesis is a form of audio synthesis that can be contrasted to either subtractive synthesis or additive synthesis. The principal difference with sample-based synthesis is that the seed waveforms are sampled sounds or instruments instead of fundamental waveforms such as the saw waves...

 combined with subtractive synthesis
Subtractive synthesis
Subtractive synthesis is a method of sound synthesis in which partials of an audio signal are attenuated by a filter to alter the timbre of the sound...

, to produce its sounds. Samples
Sample-based synthesis
Sample-based synthesis is a form of audio synthesis that can be contrasted to either subtractive synthesis or additive synthesis. The principal difference with sample-based synthesis is that the seed waveforms are sampled sounds or instruments instead of fundamental waveforms such as the saw waves...

 are used for attacks and drums, while traditional synthesis assures the sustain phase of the sounds.

The original MT-32 comes with a preset library of 128 synth and 30 rhythm sounds, playable on 8 melodic channels and one rhythm channel. It also features a digital reverberation
Reverberation
Reverberation is the persistence of sound in a particular space after the original sound is removed. A reverberation, or reverb, is created when a sound is produced in an enclosed space causing a large number of echoes to build up and then slowly decay as the sound is absorbed by the walls and air...

 effect. Successors (see below) added a library of 33 sound effects. Because of the absence of a piano attack sample, it cannot play a convincing acoustic piano sound.

Being a synthesizer rather than a wavetable device
Wavetable synthesis
Wavetable synthesis is used in certain digital music synthesizers to implement a restricted form of real-time additive synthesis. The technique was first developed by Wolfgang Palm of PPG in the late 1970s and published in 1979, and has since been used as the primary synthesis method in...

, the MT-32 is very programmable. Sounds are created from up to 4 partials which can be combined in various ways (including ring modulation
Ring modulation
Ring modulation is a signal-processing effect in electronics, an implementation of amplitude modulation or frequency mixing, performed by multiplying two signals, where one is typically a sine-wave or another simple waveform. It is referred to as "ring" modulation because the analog circuit of...

). With 32 partials available overall, polyphony
Polyphony (instrument)
Polyphony Instruments that are not capable of polyphony are monophonic.-Synthesizer:Most of early synthesizers were monophonic musical instruments which can play only one note at a time, and are often called monosynth as opposed to polysynth...

 depends on the tonal complexity of the music, and 8 to 32 notes can be played simultaneously.

The MT-32 by default does not play on the otherwise most popular MIDI channel 1 (and by consequence neither do MIDI files targeted for it), but can be reprogrammed to do this, through MIDI system exclusive messages, for example to achieve a certain level of General MIDI
General MIDI
General MIDI or GM is a standardized specification for music synthesizers that respond to MIDI messages. GM was developed by the MIDI Manufacturers Association and the Japan MIDI Standards Committee and first published in 1991...

 compatibility.

MT-32 models

Two major revisions of the MT-32 were produced. Roland refers to them as MT-32 (Old / Without headphones) and MT-32 (New / With headphones).

MT-32 (Old)

LA32 sound generation chip is an 80-pin PGA
Pin grid array
A pin grid array, often abbreviated PGA, is a type of integrated circuit packaging. In a PGA, the package is square or roughly square, and the pins are arranged in a regular array on the underside of the package...

. Control CPU is an Intel C8095-90 in ceramic DIP48 package. DAC is a Burr-Brown PCM54; the input signal having a resolution of 15 bits (see below). Line outs are unbalanced 1/4″ TS (L/R). No headphones jack.
  • MT-32 with revision 0 PCB
    Printed circuit board
    A printed circuit board, or PCB, is used to mechanically support and electrically connect electronic components using conductive pathways, tracks or signal traces etched from copper sheets laminated onto a non-conductive substrate. It is also referred to as printed wiring board or etched wiring...

    , used in units up to serial number 851399.

The PGA LA32 chip is later replaced with a 100-pin flat type.
  • MT-32 with "old-type" revision 1 PCB, used in units with serial numbers 851400 - 950499.


MT-32 (New)

Control CPU is an Intel P8098. Same DAC, but with full 16 bits of input signal resolution (see below). A stereo 1/4″ TRS headphones jack is added.
  • MT-32 with "new-type" revision 1 PCB, used in units with serial numbers 950500 and up.
  • Roland MT-100: Combination of MT-32 and Roland PR-100 (Sequencer and 2.8" Quick-Disk). While it uses a MT-32 (New) PCB, the chassis is different.

MT-32 compatible models

To target computer users, Roland released a number of CM (Computer Music) modules. They came without a LCD display and had most buttons removed. CM modules are compatible with MT-32, but feature 33 additional sound effect samples which many games took advantage of. These sound effects cannot be heard on a MT-32.
Early models share a similar design to MT-32 (New). Control CPU is an Intel P8098 and DAC is a Burr-Brown PCM54.
  • Roland CM-32L: Released in 1989, this Roland CM has only a volume knob, a MIDI message and a power-on indicator as external controls.
  • Roland CM-64: A combination of the CM-32L with the sample-based CM-32P, a cut-down "computer music" version of the Roland U-110
    Roland U-110
    The Roland U-110 is a synth module produced by Roland Corporation in 1988.-General information:Roland's answer to the E-mu Proteus, the predecessor of the more successful U-220 module and U-20 keyboard and the ancestor of the prototype T-110, the U-110 was Roland's first dedicated sample playback...

    . The CM-32P part plays on MIDI channels 11-16 which are not used by the CM-32L part.
  • Roland LAPC-I
    Roland LAPC-I
    The Roland LAPC-I is a sound card for IBM PC compatible computers produced by Roland Corporation. It basically consists of a MT-32-compatible Roland CM-32L and a MPU-401 unit, integrated onto a single full-length 8-bit ISA card. In addition to normal Roland dealers aimed at musicians, it was...

    : ISA
    Industry Standard Architecture
    Industry Standard Architecture is a computer bus standard for IBM PC compatible computers introduced with the IBM Personal Computer to support its Intel 8088 microprocessor's 8-bit external data bus and extended to 16 bits for the IBM Personal Computer/AT's Intel 80286 processor...

     bus expansion card for IBM PCs and compatibles. Includes the MPU-401
    MPU-401
    The MPU-401, where MPU stands for MIDI Processing Unit, was an important but now obsolete interface for connecting MIDI-equipped electronic music hardware to Personal Computers...

     interface.

In later models, the DAC is a Burr-Brown PCM55, and Vibrato
Vibrato
Vibrato is a musical effect consisting of a regular, pulsating change of pitch. It is used to add expression to vocal and instrumental music. Vibrato is typically characterised in terms of two factors: the amount of pitch variation and the speed with which the pitch is varied .-Vibrato and...

 is noticeably faster.
  • Roland CM-32LN: Sound module for the NEC PC-98
    PC-9801
    The NEC PC-9801, part of the PC-98 series, is a Japanese 16-bit microcomputer manufactured by NEC.- History :It first appeared in 1982, and employed an 8086 CPU. It ran at a clock speed of 5 MHz, with two µPD7220 display controllers , and shipped with 128 KB of RAM, expandable to 640 KB...

     series notebook computers, featuring a special connector for direct connection to the computer's 110-pin expansion port. Released in Japan only.
  • Roland CM-500: A combination of the CM-32LN with the Roland GS
    Roland GS
    Roland GS, or just GS, sometimes expanded as General Standard or General Sound, is an extension of General MIDI specification. It requires that all GS-compatible equipment must meet a certain set of features and it documents interpretations of some MIDI commands and bytes sequences, thus defining...

    -compatible Roland CM-300, the "computer music" version of the Roland SC-55
    Roland SC-55
    The Roland SC-55 is a GS MIDI synthesizer sound module released in 1991 by Roland. The SC-55 was the first sound module to incorporate the new General MIDI standard....

    . Released around 1992.
  • Roland LAPC-N
    Roland LAPC-I
    The Roland LAPC-I is a sound card for IBM PC compatible computers produced by Roland Corporation. It basically consists of a MT-32-compatible Roland CM-32L and a MPU-401 unit, integrated onto a single full-length 8-bit ISA card. In addition to normal Roland dealers aimed at musicians, it was...

    : C-Bus expansion card for the NEC PC-88
    NEC PC-8801
    The NEC PC-8801 was an early Zilog Z80-based computer exclusively released in Japan, where it became very popular, by NEC Corporation in 1981. It was informally called the "PC-88"....

     and NEC PC-98 series of computers. Released in Japan only.

Sound quality problems

Given the MT-32 was intended to be a relatively low-cost prosumer
Prosumer
Prosumer is a portmanteau formed by contracting either the word professional or less often, producer with the word consumer. For example, a prosumer grade digital camera is a "cross" between consumer grade and professional grade...

 product, many corners were cut in the design of its DAC
Digital-to-analog converter
In electronics, a digital-to-analog converter is a device that converts a digital code to an analog signal . An analog-to-digital converter performs the reverse operation...

 output. For example the circuitry needed to properly calibrate the DACs was omitted, resulting in distortion of the analog signal.

Despite having the capabilities of a professional synth module, the noisy output of the MT-32 caused it to be generally considered unsuitable for professional studio use, however an aftermarket modification was available from Real World Interfaces to improve the MT-32's sound quality and generally increase its suitability for professional use.

Digital overflow

The MT-32 and compatible modules use a parallel 16-bit DAC
Digital-to-analog converter
In electronics, a digital-to-analog converter is a device that converts a digital code to an analog signal . An analog-to-digital converter performs the reverse operation...

 at a sampling rate
Sampling rate
The sampling rate, sample rate, or sampling frequency defines the number of samples per unit of time taken from a continuous signal to make a discrete signal. For time-domain signals, the unit for sampling rate is hertz , sometimes noted as Sa/s...

 of 32000 Hz. In order to improve the signal-to-noise ratio
Signal-to-noise ratio
Signal-to-noise ratio is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. It is defined as the ratio of signal power to the noise power. A ratio higher than 1:1 indicates more signal than noise...

 without investing in higher-quality components, the volume of the digital signal fed into the DAC is doubled by shifting all 15 non-sign-carrying data bits to the left, which amounts to multiplying the amplitude by two, or making the signal twice as loud while keeping the noise floor constant at the analogue output.

However, if this doubled amplitude exceeds the amount that can be represented with 16 bits, an arithmetic overflow
Arithmetic overflow
The term arithmetic overflow or simply overflow has the following meanings.# In a computer, the condition that occurs when a calculation produces a result that is greater in magnitude than that which a given register or storage location can store or represent.# In a computer, the amount by which a...

 occurs, audible as a very loud popping or cracking noise that occurs whenever the original signal crosses +16384/-16384 (the value of bit 14 lost in the bit shift).

This bit shift is implemented differently between module generations:
  • In first generation modules, this bit shift is performed at the connection between the data bus and DAC:

Original (non-shifted) data bit # Connection
--------------------------------------------------------------------------
15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00 output of LA32 synth chip
15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00 input to reverb chip
15 13 12 11 10 09 08 07 06 05 04 03 02 01 00 -- input to DAC
| |
| +- most significant data-carrying bit
+- sign bit
This means that the reverb chip will not "see" the overflow noise and thus not reverberate it. However, since bit 14 is dropped completely, the effective resolution is reduced to 15 bits, and since the DAC's least significant bit is not connected at all and thus not changing with the sign, additional one-bit noise is produced, audible at low signal levels.
  • In second generation modules, the bit shift is performed at the connection between the LA32 sound generation chip and the data bus:

Original (non-shifted) data bit # Connection
--------------------------------------------------------------------------
15 13 12 11 10 09 08 07 06 05 04 03 02 01 00 14 output of LA32 synth chip
15 13 12 11 10 09 08 07 06 05 04 03 02 01 00 14 input to reverb chip
15 13 12 11 10 09 08 07 06 05 04 03 02 01 00 14 input to DAC
| |
| +- most significant data-carrying bit
+- sign bit
This means that the reverb chip will "see" the overflow noise and thus reverberate it. However, since the DAC's least significant bit is connected and does change with the sign, the sound quality is improved slightly over the earlier implementation.

To prevent digital signal overflow and its audible result, the digital output volume must be kept low enough so that bit 14 will never be used. On the first generation MT-32, this can simply be done by selecting a lower main volume on the unit's front panel, which directly controls the software main volume setting, which in turn directly translates into the amplitude of the digital output signal.
On later generation units, this does not work, as the main volume knob and the software main volume setting only modify the volume of the analogue output using voltage-controlled amplifiers and have little effect on the amplitude of the digital signal. To prevent signal overflow, each individual part's volume (controller #7) must be kept low instead.

A third party solution

In the period of 1989 to 1993, Robin Whittle of Real World Interfaces offered aftermarket modifications to the MT-32 to address its sound quality issues, as well as improve the functionality of the reverb unit, provide discrete analog outputs for the internal reverb send and reverb return, and provide battery backup of the MT-32's settings.

According to documentation written in 1990, these modifications were only available for the first-generation MT-32, and not the later "headphone" model or any of the other MT-32 derivatives.

Note that the RWI modifications were intended for those using the MT-32 professionally, and may cause some minor compatibility issues with video game soundtracks intended for a stock MT-32. In particular the changes to the reverb unit functionality will likely cause an RWI modified MT-32 to render reverb differently than intended, with possibly detrimental effects.

Compatibility problems

First generation units, having control ROM versions below 2.00, require a 40 millisecond delay between system exclusive messages. Some computer games which were programmed to work with the compatible modules (see above) or later ROM versions that do not require this delay, fail to work with these units, producing incorrect sounds or causing the firmware
Firmware
In electronic systems and computing, firmware is a term often used to denote the fixed, usually rather small, programs and/or data structures that internally control various electronic devices...

 to lock up due to a buffer overflow
Buffer overflow
In computer security and programming, a buffer overflow, or buffer overrun, is an anomaly where a program, while writing data to a buffer, overruns the buffer's boundary and overwrites adjacent memory. This is a special case of violation of memory safety....

 bug, requiring turning the unit off and on. However, some games were designed to exploit errors in earlier units, causing incorrect sound on later revisions.

Also, some games were written to use instruments not found in the MT-32 models, and require a compatible module, such as a CM-32L, for proper sound playback.

Music for PC games

Despite its original purpose as a companion to other professional MIDI equipment, the MT-32 became one of several de-facto standards for PC
IBM PC compatible
IBM PC compatible computers are those generally similar to the original IBM PC, XT, and AT. Such computers used to be referred to as PC clones, or IBM clones since they almost exactly duplicated all the significant features of the PC architecture, facilitated by various manufacturers' ability to...

 computer game publishers. Sierra On-Line, a leading PC game publisher of the time, took an interest in the sound-design of its PC games. Sierra secured a distribution deal to sell the MT-32 in the US, and invested heavily in giving its game titles (at the time) state-of-the-art sound by hiring professional composers to write in-game music. King's Quest IV, released in 1988, was the first Sierra title with a complete musical soundtrack scored on the MT-32.

The MT-32 with a necessary MPU-401 interface cost $550.00 to purchase from Sierra when it first sold the device. Although the MT-32's high price prevented it from dominating the end-user market of gamers, other PC publishers quickly followed Sierra's lead, expanding the role of music in their own game titles with Roland supporting the industry by releasing CM modules for computer users. The MT-32 remained the gold-standard for musical composition well into the early 1990s, when the game-industry began to shift toward General MIDI
General MIDI
General MIDI or GM is a standardized specification for music synthesizers that respond to MIDI messages. GM was developed by the MIDI Manufacturers Association and the Japan MIDI Standards Committee and first published in 1991...

 and later CD Audio.

The proliferation of the General MIDI
General MIDI
General MIDI or GM is a standardized specification for music synthesizers that respond to MIDI messages. GM was developed by the MIDI Manufacturers Association and the Japan MIDI Standards Committee and first published in 1991...

 standard, along with competition from less expensive wavetable-based soundcards, led to the decline of musical soundtracks using the MT-32's proprietary features. Games that played General-MIDI tracks on the MT-32 initialized the MT-32's sound bank to approximate the General MIDI Level 1 (GM1) specification, but avoided any of the MT-32's hallmark music-synthesis features, adhering to GM1's rather limited set of controllers.

See also: List of MT-32-compatible computer games

Emulation

Due to the popularity of the MT-32 as a music playback device for PC games, many modern sound cards provide a simple "MT-32 emulation mode", usually realized by way of a sound mapping comprised either of General MIDI
General MIDI
General MIDI or GM is a standardized specification for music synthesizers that respond to MIDI messages. GM was developed by the MIDI Manufacturers Association and the Japan MIDI Standards Committee and first published in 1991...

 instruments rearranged to roughly represent the MT-32's preset sound bank, or of samples directly recorded from the original unit. Results are often considered poor, as the sampling technology used can not reflect the pitch- and time-variable characteristics of the original synthesizer technology, with the programming of custom sounds (see above) not being supported at all.
One exception is the Orchid SoundWave 32 card released by Orchid
Orchid Technology
Orchid Technology was a privately held company founded by Le Nhon Bui in 1982. The company's original flagship product was its PCNet card, a 1 megabit-per-second LAN card for IBM PCs and clones. Notably, the acronym LAN is the Vietnamese word for "Orchid"...

 in 1994, whose on-board DSP
Digital signal processor
A digital signal processor is a specialized microprocessor with an architecture optimized for the fast operational needs of digital signal processing.-Typical characteristics:...

 allowed for a more faithful reproduction of the original sound characteristics.

More recently, there have been attempts at emulating the LA synthesizer technology in software using images
ROM image
A ROM image, or ROM file, is a computer file which contains a copy of the data from a read-only memory chip, often from a video game cartridge, a computer's firmware, or from an arcade game's main board...

 of the original PCM and control ROM
Read-only memory
Read-only memory is a class of storage medium used in computers and other electronic devices. Data stored in ROM cannot be modified, or can be modified only slowly or with difficulty, so it is mainly used to distribute firmware .In its strictest sense, ROM refers only...

s. The most notable of these emulators is the Open Source project, Munt, which currently tries to emulate the MT-32 hardware by way of a WDM driver for Windows XP
Windows XP
Windows XP is an operating system produced by Microsoft for use on personal computers, including home and business desktops, laptops and media centers. First released to computer manufacturers on August 24, 2001, it is the second most popular version of Windows, based on installed user base...

. It is also incorporated into ScummVM
ScummVM
ScummVM is a collection of game engine recreations. Originally designed to play LucasArts adventure games that use the SCUMM system , it now also supports a variety of non-SCUMM games by companies like Revolution Software and Adventure Soft. It was originally written by Ludvig Strigeus...

, an Open Source adventure game
Adventure game
An adventure game is a video game in which the player assumes the role of protagonist in an interactive story driven by exploration and puzzle-solving instead of physical challenge. The genre's focus on story allows it to draw heavily from other narrative-based media such as literature and film,...

 interpreter, as of version 0.7.0. Munt is based on an earlier MT-32 Emulation Project, which was the source of a short-lived legal squabble over distribution of the original ROM images with Roland Corporation
Roland Corporation
is a Japanese manufacturer of electronic musical instruments, electronic equipment and software. It was founded by Ikutaro Kakehashi in Osaka on April 18, 1972, with ¥33 million in capital. In 2005 Roland's headquarters relocated to Hamamatsu in Shizuoka Prefecture. Today it has factories in Japan,...

, who manufactured the MT-32 and claims copyright on the ROM's data.

Roland has recently been offering its own emulation of classic synthesizers, notably of the D-50.

External links

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