Wednesday, July 29, 2015

Yamaha's TG100/OPL4 Connection

Today I am excited to publish the first blog entry on this blog from a guest blogger.  This blog entry was written by my good friend Cloudschatze.  Except for a few minor edits, the remainder of this blog entry comes directly from him :


Released in early 1992, the inauspicious Tone Generator TG100 marked Yamaha's initial foray into the burgeoning world of General MIDI - a market that was, at the time, wholly defined and dominated by Roland's then year-old Sound Canvas SC-55.

At a glance, the TG100 (along with its display-less DTM counterpart, the CBX-K3), is a 28-note "Advanced Wave Memory" tone generator, containing 192 instrument voices, 64 user voices, 10 drum kits, and featuring a custom reverb DSP.  Promoting its usefulness in a laptop-connected, portable environment, the TG100 is also one of the first musical instruments to feature serial port connectivity, effectively negating the need for a dedicated host-based MIDI interface like the MPU-401.  Aesthetically, the TG100 is smaller than photos might suggest and unsubtly seems to borrow certain design elements from Roland's earlier MT-32.

Drawing comparisons with the SC-55, Yamaha's TG100 similarly satisfies the General MIDI requirements, while likewise providing a superset of features to both enhance the experience, and impart a degree of compatibility with non-GM-conforming sequences.  While a GM device by default, the TG100 provides two alternate modes of operation, offering instrument/drum-map compatibility with either Yamaha's own "Disk Orchestra" (Clavinova) units, or with Roland's CM-64.  An "RX" drum kit rounds-out the mix of versatility, providing a layout compatible with Yamaha's RX-series drum machines.

Enhancements over the SC-55 include an extra four notes of polyphony, a larger waveform ROM set (4MB vs. 3MB), and the traditional synthesizer/ROMpler-esque ability to create up to 64 user-defined instruments like the MT-32.  Yamaha's Windows 3.1-based, "WinTiGer" editor lends some ease to the instrument creation process, revealing an architecture reminiscent of the latent QS300 functionality of Yamaha's earlier XG tone generators.




Oh, British humor...

Given that TG100 units routinely sell for under $50 these days, it would be reasonable to think that such a purchase could be a no-brainer for anyone looking for an external General MIDI playback device for retro-gaming, right?

In my opinion, no, and here's why:

It's not a Sound Canvas. 

No kidding, right?

By design, the General MIDI requirements offered neither suggestion, nor restriction, on how compatible devices should sound.  General MIDI required little more than Program Change #0 sound like a piano, Program Change #23 like a harmonica and so on.  Implementers were left with creative interpretation regarding the specific synthesis methods and waveforms used to generate these sounds, and, of great significance, their volume and envelope levels.  Because each implementer made their own unguided choices on how each instrument would sound, there was an unfortunate amount of playback variance to be had between the first GM-compatible devices.
Given Roland's well-managed head start, you'll find that most GM soundtracks were authored with, or for, the de-facto standard GM device that was the Sound Canvas.  This fact was not lost on Roland's competitors, who, in turn, designed subsequent GM-compatible offerings to better imitate the characteristics of the SC-55.  Unfortunately, for early devices like the TG100, a majority of non-native sequence playback - in-game or otherwise - tends to come across as undesirably unbalanced.

My opinion of its PC gaming suitability aside, as a compositional tool, or even just a cheap serial-to-MIDI converter, an inexpensive TG100 might be well worth experimenting with.  Regrettably, the gaming-focused comparisons available on YouTube, while important for that purpose, tend to be poorly representative of the TG100 as a whole.  As with other GM-compatibles, you really need to hear native compositions to get a complete impression of the TG100's tonal character.

Michael Walthius, the "Keyboard Wizard," composed with the TG100 for several years, and perhaps his music provides the best examples of the TG100's potential:

"Demons"
"Dreaming in Stereo"
"Echoes"
"Eternium"
"The Ultimate Life"

These pieces demonstrate some of the TG100's strengths and weaknesses with its instrument patches.  To be sure, the electric guitars are wildly unconvincing, and, owing to its less-complex engine, the synth leads and pads are remarkably shallow and uninspiring.  Conversely, the acoustic/orchestral instrumentation, and drum kits in particular, are of mostly decent quality.  Overall, and when properly composed for, I feel that the TG100 is able to provide a comparable counterbalance to Roland's SC-55, which the recordings hopefully demonstrate.

Now, interestingly enough, while most of the major General MIDI module releases have direct ISA sound card or waveblaster daughterboard-format counterparts, Yamaha's TG100 seems to be the odd exception.

Or, is it..?

Although Yamaha dominated the low end of PC music playback with its OPL2 and OPL3 chips, found on innumerable sound cards, the company continued to innovate to meet the need for more advanced but still cost-effective PC music reproduction.  Designed around 1992/1993, but entering full production in early 1994, Yamaha's OPL4 combined 20-voice, OPL-3 compatible FM synthesis, and 24-voice, PCM "Wave Table" synthesis in a single IC, the YMF278B.  ROM samples for the PCM synthesis engine are contained on a separate chip.  Unsurprisingly, a comparison of the TG100 and OPL4 PCM wavetable synthesis parameters shows more than a few similarities.  In fact, take the TG100, reduce its capabilities down to the most basic General MIDI requirements (24-voice polyphony, 128 capital tone instruments, 1 drumkit, no effects), and you end-up with something uncannily duplicated by the YMF278B + (2MB) YRW801 sample ROM combination, when used in conjunction with Yamaha's original instrument definition data specific to that pairing. 

The similarity between the TG100 and the OPL4 is striking.  Hearing is certainly believing, as demonstrated with playback of the same Michael Walthius compositions with Mediatrix' OPL4-bearing AudioTrix Pro soundcard.



"Demons"
"Dreaming in Stereo"
"Echoes"
"Eternium" Notice the lacking "Analog Kit," as compared to the TG100 version.
"The Ultimate Life"

The OPL4 playback in the above recordings was accomplished through use of MediaTrix' earlier, "PLAYMIDI" utility, which contains a direct-write, standalone MIDI interpreter, and utilizes Yamaha's original patch information derived from the TG100. While these particular AudioTrix Pro OPL4 hardware recordings bear substantial similarities to the TG100 recordings, MediaTrix' version 2.0 initialization firmware and drivers incorporate patch modifications by Fat Labs, successfully providing a more balanced approach to playback, but breaking the balance level compatibility with the TG100 in the process.  As a result, the same MIDI files do indeed sound different when played through the AudioTrix Pro's MPU-401 interface, or in Windows.  Similarly, Yamaha's YMF278B-bearing SW20-PC soundcard, and the later, ROM-integrated OPL4-ML(2) chipsets, contain both revised ROM sample sets and patch data and will not sound the same compared to the TG100 or the AudioTrix cards.

At the end of the day, the OPL4's TG100-based lineage seems pretty clear - a connection that seems to have gone almost wholly unnoticed by the entire Internet.

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