Roland MT-32

Like the Roland D-50 Linear Synthesizer, it uses Linear Arithmetic synthesis, a form of sample-based synthesis combined with subtractive synthesis, to produce its sounds. Samples 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.[1] It also features a digital reverberation effect.[1] 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.

Sounds are created from up to 4 partials which can be combined in various ways (including ring modulation). With 32 partials available overall, polyphony depends on the tonal complexity of the music, and 8 to 32 notes can be played simultaneously.[1]

The MT-32 by default assigns its parts 1~8 and R(hythm) to respond on input MIDI channels 2~9 and 10 respectively. By consequence, MIDI files using the popular channel 1 or the other channels 11~16 cannot have those parts played on the MT-32. However, the MT-32's melodic parts can be shifted down to respond to channels 1~8 using a button combination or through MIDI system exclusive messages, enabling improved compatibility with non-MT-32-specific MIDI sequences.

Additionally, in 1993 Roland released the "GM2MT" SysEx pack, which can be used to reprogram the MT-32 and compatibles to match General MIDI specifications as closely as possible.[2] 64 of the 128 patches (the limit of possible variations) are completely new or modified sounds, with additional sounds having been added to drum channel 10. Despite this, compatibility with GM is still limited by the lack of parts (9 on the MT-32, 16 per GM specification) and reversed panpot compared to MMA MIDI specifications. The utility was predated by a pack called "MT32GS", released by Mike Cornelius in 1992.[3] The CM-Panion, by Gajits Music Software, was an Amiga editor which worked with the MT-32.[4]

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).

Back view of MT-32 (Old)

Top view of MT-32 with cover removed (Old, Rev. 1 PCB)

MT-32 (old)

The LA32 sound generation chip is an 80-pin PGA. The control CPU is an Intel C8095-90 in ceramic DIP-48 package. The digital-to-analog converter (DAC) is a Burr-Brown PCM54; the input signal having a resolution of 15 bits (see below). Line-outs are unbalanced 1/4″ TS phone connector (separate left and right channels.) No headphone jack.

• MT-32 with revision 0 PCB, used in units up to serial number 851399.

The PGA LA32 chip is later replaced with a 100-pin QFP type.

• MT-32 with "old-type" revision 1 PCB, used in units with serial numbers 851400 - 950499.

Back view of MT-32 (New)

To target computer users, Roland released a number of CM (Computer Music) modules. They came without an 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 an 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. The CM-32P part plays on MIDI channels 11-16 which are not used by the CM-32L part.
• Roland LAPC-I: ISA bus expansion card for IBM PCs and compatibles. Includes the MPU-401 interface.

In later models, the DAC is a Burr-Brown PCM55, and vibrato is noticeably faster.

• Roland CM-32LN: Sound module for the NEC PC-98 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-compatible Roland CM-300, the "computer music" version of the Roland SC-55. Released around 1992.
• Roland LAPC-N: C-Bus expansion card for the NEC PC-98 series of computers. Released in Japan only.

Given the MT-32 was intended to be a relatively low-cost prosumer product, many corners were cut in the design of its DAC output. For example, the circuitry needed to properly calibrate the DACs was omitted, resulting in distortion of the analog signal.[5]

Despite having the capabilities of a professional synthesizer module, the noisy output of the MT-32 caused it to be generally considered unsuitable for professional studio use, although it was considered sufficient for use as the sound engine within other Roland prosumer products of the period. For example, the first generation of E-series home keyboards produced by the company, the first being the E-20 (and its associated modular version the RA-50 arranger), use a highly modified MT-32 motherboard. 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.[5]

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 synthesizer chip
15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00  Input to reverberation 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

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 synthesizer chip
15 13 12 11 10 09 08 07 06 05 04 03 02 01 00 14  input to reverberation 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

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 to lock up due to a buffer overflow 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.

Despite its original purpose as a companion to other professional MIDI equipment, the MT-32 became one of several de facto standards for PC 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 popular for musical composition well into the early 1990s, when the game-industry began to shift toward CD Audio.

The proliferation of the General MIDI standard, along with competition from less expensive "wavetable" sample-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.

Due to the popularity of the MT-32 as a music playback device for computer 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 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 Technology in 1994, whose on-board digital signal processor (DSP) 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 of the original PCM and control ROMs. The most notable of these emulators is the open-source project Munt,[10] which emulates the MT-32 hardware by way of a virtual device driver for Microsoft Windows, or a virtual MIDI device for OS X, BSD and Linux. It is also incorporated into ScummVM, an open-source adventure game interpreter, as of version 0.7.0. Munt is based on an earlier MT-32 Emulation Project,[11] which was the source of a short-lived legal argument over distribution of the original ROM images with Roland Corporation, who manufactured the MT-32 and claims copyright on the ROM's data.

Roland offers emulation of classic synthesizers via the Roland Cloud subscription service. Support for the D-50[12] was notably added in June 2017.[13]

Wikimedia Commons has media related to Roland MT-32.

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