Again, there is no windows version. It has everything to do with what kind of MIDI device the music is being played on. The default one emulated by DOSbox is not of the highest quality, but it is possible to change it as explained earlier.

Ok, so...

The Amiga's audio is 4 channels of 8-bit digital (sampled) audio. Everything must be sampled, and then played back. It has no internal synthesis engine (no analog, no FM, etc.) There are tricks one can do to synthesize sounds, (like tiny samples cycled at audio rates) Look up Amiga Chip Tunes to get an idea of this, but this is unrelated to your questions. In many cases the digital audio on the Amiga did in fact sound better (down to personal taste really) because it was using "real" sampled sounds before most other home computers and early PCs. The sample rate was determined by the sample's frequency being played, so it even had a somewhat unique sound (and better) than other sample playback at the time, using static sample rates. Anyway, the music you hear on the Amiga is often samples of "real" instruments, synthesizers, percussion, so despite its low sample rate and bit-depth, it sounded more real than other methods like FM synthesis. This means the sound is as good (minus sample quality limitations) as the source of the sound being recorded. If you sample a high-end analog synth, it's going to sound pretty good. If you sample a toy-Casio keyboard... maybe not so much. :) It also means there is a lot less flexibility of manipulating the sound on the fly. With FM or analog synthesis you can modulate the sound while it's playing in many possible ways. With samples, you can pretty much modulate the speed it's playing back, and the amplitude it's played back at. (plus a few little tricks, but nothing quite as expressive as other synthesis methods...)

The PC is all over the board. The Adlib card (first decent sound card) was FM synthesis. It used either a Yamaha YM chip or possibly an OPL. (some of these IC models overlapped) This is the typical 80s / early 90s PC game music that you'd hear, and is similar to some arcade games, the Sega Genesis, etc. It has characteristically "ringy" or bellish type sounds, unrealistic percussion, and most people tend not to like it all that much. This is where personal taste comes into it though. I actually prefer most synthesis methods to digital samples (in most cases anyway). It's not a shoddy reproduction of an acoustic instrument, it's its own sound, and taken as such it can be very charming. I have fond memories of these sounds, and have hear some rather impressive arrangements using FM synthesis. I still write music using it these days.

In the late 80s / early 90s, synths like the MT-32 came out. It uses a combination of sampled orchestral instruments, and it's own "Linear Arithmetic" synthesis, which is a very primitive form of digital synthesis. The combination of these allowed not only somewhat orchestral sounding music scores, but also sound effects to be created. This is where this side of PC music started getting interesting. The MT-32 is probably the pinnacle of DOS game music (if you're less into FM). Shortly after this the General MIDI standard kind of took over with things like the Sound Canvas, and many PC sound cards started including a set of General MIDI compliant sample-sets. General MIDI is a specification for basic MIDI functionality as well as a basic set of instrument sounds and how they map (which order they're accessed, and given a patch ID.) So you could always count on patch-1 being a grand piano, etc. The fidelity of these sampled instruments improved significantly, in that they sounded more like their real-world counterparts. (IMO it also made them sound more generic) However, music started sounding more and more like movie scores (to some degree anyway). That's where a lot of people think the high-point was at the time. However, General MIDI didn't have a good way to play back sound effects by itself. Later there were cards that let the developer load in custom sample sets, and things like this, but it still wasn't that great IMO.

Many games would allow you to use two. General MIDI or General Sound (GS was an enhanced version) and a SoundBlaster or similar card. This way the GM device would play music, and the second card would play sound effects. Either FM or digital samples. This was great, however it was often tricky to get both to play nicely together. Then there were also a lot of cards that claimed full compliance, like the Gravis Ultra Sound, or the AWE32/64, but their implementations didn't always work perfectly, and you'd either be left with no GM music, or no digital sound because the game didn't recognize it as two perfect separate devices.

Back to Ultima 6/7/8 for a minute. If you played these games on the MT-32, or GM+SB setups, then their music was FAR better than the Amiga version. If you like FM synthesis like I do, just playing on an Adlib or SoundBlaster would still be better than the Amiga. If not though, the Amiga probably sounds better to your ears. Don't get me wrong. The Amiga had some REALLY REALLY good music. Especially scene-demos that someone else mentioned above. In the right context it was really (and still is) quite impressive. I still listen to a lot of MODs these days. I just prefer synthesis to samples in general.

With a little extra hardware (a $20 USB Midi interface and a real MT-32) DOSBox will actually play through the real MT-32. So you can do it that way.

Some versions of DOSBox have MT-32 emulation, and are actually **pretty close** to that.

You can also load a GM/GS sound-bank (I second Fluid-Synth mentioned above by someone else) and a really nice sound bank. There are some really nice ones out there. This will give excellent music, but sound effects are going to sound like drums and pianos :D unless the game supports an additional digital card like the SoundBlaster. DOSBox will provide both to the game. This should work with U7/U8 but I'm not sure if U6 supported two cards. I seem to remember it didn't.

In this case, I recommend a real MT-32+USB MIDI Interface, just emulating SoundBlaster only and using FM music. GM only can be a bit distracting when it tries to do sound effects using instruments.

It's definitely worth experimenting though, and even spending a little money if needed, as this will also benefit you with other DOS games. Wing Commander has great GM/MT/FM music for example. At the right settings even just DOSBox emulations sound very good. It might take a bit of effort to get it working though.

Sorry for the book, but as you can tell this all interests me. (I design synthesizers on the side.) :)

There are other types of synthesis used in game consoles and home computers too, that also have their own charm, but those are a bit outside the scope of DOS games. :)

One more item. If you're playing Ultima 6 / 7 / 8 there are some really cool alternative ways to run them.

Ultima 6 - Nuvie
Ultima 7 - Exult
Ultima 8 - Pentagram

These are modern "engines" that run the game data from these games. They include a lot of flexibility and features to run the games. Graphical scalers, many sound and music options, easy configuration, developer consoles, game fixes (bug fixes that weren't in the original games) etc. I HIGHLY recommend using these. You'd still buy your games from GOG or use your original discs, but use the above applications to run them.