since there is very little information on this module out there i thought i'd do a little writeup from the standpoint of GM playback. first, some basic info: https://soundprogramming.net/synthesizers/kawai/kawai-gmega/

the GMega shares its hardware with the K11 keyboard and was likely released in early 1993, though interestingly some of the chips can have 1992 and even 1991 date codes. 32-part multitimbrality and 32-voice polyphony was certainly top of the line for a 1993 GM unit, as was the 6 MB sized ROM, which AFAIK was only matched by the korg 05R/W at the time. there is also the possibility to link two GMegas together, with a dedicated option in the menu for this. an 18-bit DAC is claimed in the manual and demo song text, unlike the 16-bit stated in the link above, and the 44.1 khz sample rate is also better on paper than the sound canvas series' 32 khz. a mac-only serial port is present. apart from the standard GM patches, extra drumkits are also onboard and are compatible with the SC-55.

in terms of effects, reverb is there but chorus is missing. like on the SC-55 a delay can be applied to the reverb, which is globally activated on the GMega by default, though it's a fairly light delay effect and can be turned off. the reverb intensity setup by standard MIDI controls (CC#91) is rather odd: instead of being adjustable from 0-127, every channel has a an "effect level" with hi or lo setting, with the lower half of CC#91 being mapped to lo and the upper half to hi. it's not well explained in the manual what this exactly means, but from what i can tell lo simply disables reverb altogether for that channel, while hi uses the (roland sysex incompatible) settings in the menu. factory settings for all channels are "hi", so if CC#91 isn't sent there always will be quite a bit of reverb by default. this is in contrast to some other modules like the SC-55 that can actually set reverb to 0 in certain circumstances.

regarding front panel controls, this has to be one of the worst designs of the day. there is a lack of dedicated controls so the cursor needs to be switched around, and then inputs have to be made with the big increment dial, even confirming certain options which is awkward, and the dial seems to be prone to wearing out over time and working less reliably. in terms of sounds, they generally are of a higher quality than the SC-55 and especially the TG100, however DOS game music in particular will not necessarily sound better than on the SC-55, mainly due to instrument volume balance being often rather different. the standard drumkit partly takes after the room kit, which may be appreciated. main strong points in my book are the guitars, both acoustic and electric, which can make certain tracks sound very good. synth basses have a very unique sound as well but are also quite loud. conversely, some of the synth pads can be bit quiet. the synth drum patch has to get a special mention for being all but incompatible with what roland did for the SC-55.

now, for the problems with the GMega: for one, the unit does not react to GM reset sysex whatsoever - instead two buttons are marked on the front panel that have to be pressed simultaneously. since the TG100 came out earlier and does process GM reset sysex, this is quite an annoying oversight. apparently with the later GMega LX they fixed this issue (or rather they had to, due to a lack of front panel controls). as expected, GM resets do not affect parameters that are specific to the GMega, like the reverb settings; these can be restored by performing a factory reset instead.

the bigger issue though is that with certain MIDIs the GMega does not seem to perform like other 32-voice capable hardware. compare heretic's E1M1, which can be hardly considered a heavy MIDI track, on the TG100 and the GMega:

https://www.wavetable.nl/files/comparison/gam … %20TG100%5D.mp3
https://www.wavetable.nl/files/comparison/gam … %20GMega%5D.mp3

from 0:54 onward, drums and strings quite noticeably cut out on the GMega, while the TG100 doesn't really break a sweat, despite releasing earlier and only having 28-voice polyphony. unfortunately, the GMega has problems like this with quite a few MIDI files. somewhat related, triggering too many notes at once, sometimes even as few as 4 or 5, tends to cause timing issues in the playback that i never noticed on any other synth. i was not able to pinpoint what exactly is the cause of these issues; looking through the manual, some patches do use two voices, but there isn't much difference to other GM hardware there. it does seem that turning off the percussion channel helps more often than not. perhaps either voice resources are spread around internally in a weird way or, more likely, the on-board CPU can't keep up with too rapid MIDI messages; for instance page 93 in the manual asks to not switch effect types during song playback, and the menu can in fact lag heavily during MIDI file playback. unlike other devices that used off-the-shelf parts, the CPU here is either integrated with the main chip or another part with custom markings.

overall, it's an interesting unit with some unique characteristics for the time, but also has problems that aren't usually present on other GM hardware.