ST version was done with lot of efforts to make it work on 512K machines, while Amiga v. needs 1 MB RAM. They used really every available RAM space, and samples were in pretty compact format. There are 21 samples in DM, and total length is only 17 KB. For instance same sample is used for rat and dragon attack. PC version has 35 different samples. Chaos Strikes Back uses complete same sample set as ST DM.
I kept original sample count, because adding new ones would need really lot of changes in code, and probably hundreds of hours work. Beside better sound quality, game speed is little better too.
Tutorial would be: you need good knowledge of 68000 asm, Atari ST(E) and plenty of time. No simple recipes. In case of DM and CSB big help was that there is lot of tools and files available, so good quality samples too. I was able to extract original samples with names using special tool (DMEXTRACT - what I used to make loading faster too, some years ago). DM was really popular, and is probably game what is most examined, modded, done most clones, etc.
I'm in process of improving sound in Prince of Persia. Samples during play are already redone (with STE DMAA), and now no slowdowns during sound effects. Samplerate in POP is bigger than in DM, but that makes bigger slowdowns. However, it was good for me, because couldn't find good samples online, so I converted original ones. All it is pretty different in POP than in DM. But harder part is yet to do: need to find a way for quality music playback, what will not need plenty of RAM. I'm already at edge of 1MB RAM required. May be that will just use direct hard disk read and longer sample file for title music, and ingame, shorter tunes will be in RAM - most likely 2MB RAM will be needed, without GAMEX. Quality sound has it's price. But I guess that most of people has already 4MB in their STEs.
Famous Schrodinger's cat hypothetical experiment says that cat is dead or alive until we open box and see condition of poor animal, which deserved better logic. Cat is always in some certain state - regardless from is observer able or not to see what the state is.