Jackie Chan and Final Soldier sound alike too.
Jackie Chan, Super Star Soldier, Soldier Blade, Aldynes, Final Solder, Neutopia 2 and some others all seem to have the same instrument suite.
From what I've noticed, a popular setup uses 3 channels for a chorus or chord, 1 for bass synth, and 1 for drum kit. 4 channels for chorus effect is popular too (for that part of a song). That gives you around 3 instruments at any one time. The games that seem to stand out are the ones that sound like they have more instruments at a time. Though instrument sound also have a lot to do with it.
Splatter House: Very good PCE music. I really like the instruments and the composition sounds more complex than your average PCE game - or at least technically.
The technical side(for the curious, otherwise just skip it):
On the PCE, you have simple tones made from custom waveforms. The timbre of the instrument sound comes from the waveform you define (usually basing it on sine, triangle, square, pulse, saw thooth, etc). A very rare occasion games like Bloody Wolf swap out the waveform during the instruments note duration. An instrument note duration might have 3 to 6 swaps of the waveform. This is probably emulating some other effect done on a different type of audio hardware.
If you want to add any other sort of characteristic to the instrument sound, you have to do it with software with (AM) Amplitude modulation, (LFO) low frequency oscillation, frequency slides/bends, and ADSR envelopes. All the games I've looked at do these very things, but at low cycle rates like 60hz or below. Some games don't even do this, but instead just chorus simple tones together with decay(rapid or slow rate of fade).
Some instrument sounds need 2,3, or even 4 channels to make or replicate a more complex instrument sound. Though that lowers the number of instrument sounds at a single moment in time. You'll notice some songs will drop into a part of the song that uses this more complex instruments sound during a break, solo, or slow down and then switch bank to the other instruments (I'm not sure what this is called in the music composing). world).
Making unique or even just decent instruments for PCE isn't easy. Other than using some one else' library of sounds, you really need to know what you're doing on the PCE audio wise. It's amazing that audio composers back in the day used stuff like MML to make their music.
Some things that weren't really taken advantage of.
PCM samples. The PCE can do them with ease and at different sample rates. Unless you're really clever, you were limited up to 7khz. Still, that's quite enough sample rate for decent sample types. Just look at SF2 voices and voices are much more *unforgiving* to sample rate and bit depth than instruments and other sounds. Not only that, but you have up to 6 channels you can output on. Listen to Batman. The bass guitar sounds pretty good. It also uses two channels for samples instead of one like other games.
10bit vs 5bit. It takes two channels to make a single 10bit audio channel. Sounds a bit wasteful until you realize that you can software mix two 9bit samples on a single pseudo 10bit channel. Is channel mixing hard or complex or require a lot of resource? No. It's really easy to do; you just add sample 1 to sample 2 on a per 9bit fetch. One simple add. You can take this even further by adding four 8bit samples to make a final 10bit output. That gives you 8 audio channels: 4 PCMPSG and 4 8bit PCM channels.
But wait a minute.. don't samples take a lot of memory. Yes and no. Some instruments have a unique part, then a repeating part with a slow fade. Look at a bass synth. You have the "attack" but the decay is the same pattern over and over. You can exploit this by storing just the attack and pattern part, and loop the pattern part while fading it. Many synth sounds have such properties. Even if you didn't take advantage of this, you can reuse the same samples in other songs in the rom/game. At 8bit resolution, it takes 7k to store 1 second of audio. That's really not that bad at all. Setting aside 64k or 128k (1 megabit) just for samples is pretty reasonable especially if it's a rom.
ADPCM: It's been used in a handful of games. Fiend Hunter and Cyber City OEDO 808 come to mind. Another channel and no cpu resource for playback with its own sample memory and compression? What's not to like? Apparently is was too good for most PCMPSG composers I guess. If you've filtered (prep'd) the audio before ADPCM conversion or have a really high resolution source, then it sounds great. The really great thing about ADPCM unit is that you can easily do beat loops and multiple of them in sample ram for easy access too. And yet no game has even done this. Pitty. Oh and I forgot to mention that ADPCM is available to hucards. It's definitely possible to have the hucard/rom detect the ADPCM unit and use it if found.
FM and other synth processing: Is FM even possible on the PCE? Yes, but a little bit more... limiting. There is an actual FM setup for channel 1/0. It's label as LFO, but it can operate in the FM range (human audible frequency range) instead of low frequency like 60hz. But what I'm referring to is a software method. FM works by having two waveforms, like sine wave for instance. One of them is a carrier - or the output. Since it's a plain jane sinus tone, it lacks any characteristic or timbre. It's just a tone. The second waveform (lots of early or low end FM chips only used sine wave) changes the frequency of the tone - rapidly up and down like a swing. This gives the tone timbre. There are ratios that the two waveforms must run at, otherwise they out out of tune or give you artifacts (beyond the scope of this post). The volume of the frequency modulation carrier effects the brightness of the timbre of the carrier. That famous "bleeoouuaaarrrrrwwwww" sound from bewildered FM composers comes from sliding the volume of the modulation wave from one end to the other. This is basic FM. Add in an ADSR envelope that controls the "volume" of a modulating waveform and you get a nice synth-y sound. It gets more complicated on more complicated synths (duh). You can have multiple modulators (yamaha calls them "operators") chained and/or linked in series and some feeding back into themselves.
So how does all this relate to the PCE? Well, the PCE has a TIMER. It can be set to a number of frequencies, but what we're interested in is the highest setting - 7khz. If we modulate the frequency of a PCE channel at 7khz, then we have frequency modulation. We use multiple 8bit/8bit fixed point math counters to get multiple fine resolution timers just that one timer setting of 7khz. So what are some of the limits? The PCE's audio frequency system is one. It uses a period system instead of frequency system. These period values are converted to frequency rates which is what you want (that's how we get note accurate tones). The problem lies in that fact that the higher in octave you go, the less in between frequencies are programmable between notes because of this period system. This means you don't have a fine control over the frequency swing. There are clever ways around this (also beyond the scope of this post), but it means you need to give up a little fidelity of a waveform. Still, this technique yields *much* more variation and possibilities for PCE instruments. Also, this doesn't come cheap in the CPU resource department. And so it's not really a good idea to try and do this for more than 4 channels and still have enough resource left for something like a shooter. For RPGs and puzzle games, you can go to town and add multiple pseudo operators
You can even generate entirely new channels all in software and out put them mixed as PCM. Crazy stuff
Another thing related to the high frequency software timers. You can do high frequency amplitude(volume) modulation. And "sync" - where you restart the channels waveform playback pointer set to a fine resolution timer. It makes for some interesting effects and sounds. Combined both for a low-pass filter effect.
The PCE audio system wasn't pushed to its limit, though some fantastic audio was composed for it. IMO - working with the PCE audio is much more complicated than your standard FM sequencer. Quality of the instruments depended on the driver written for it.
An observation of the PCE CD addon: It's clear that NEC handled the design of the CD base unit. It uses NEC MCU (custom processor) to control the CD drive and ADPCM unit. The detachable CD unit is the same unit for the NEC computers. FM was fairly popular inside of japan and NEC used FM chips inside in there line of PCs. Even the MSX was given FM upgrades (and the SMS too). I'm really surprised NEC didn't include a low cost FM chip in the CD base unit.
