Most people believe that digital sound is about 1's and 0's. To a certain extent, it is. But, the sound quality can vary. I did considerable amount of research before I rebought Black Sabbath's first six albums on cd. I was looking for a raw, yet dynamic sound. The crucial choice fell on the Castle Communications releases from the 1980s. Wow! These releases blows you away. I have one negative remark. The ugly blob on the cover showing that a live track is included. It contaminates the stylish artwork. I'm not an expert on audio, but this what I know. The sound quality follow the 80-15-5 rule. 80 percent can be attributed to the actual recording. Not only the spatial conditions, the recording gear used and the placement of microphones. The performance and interplay between the musicians are equally important. That's why AI-generated music fail to be beat humans. AI can steal and imitate, but never create. The next step is mixing. Audio mixing is the process by which multiple sounds are combined into one or more audio channels. In the process, a source's volume level, frequency content, dynamics, and panoramic position are manipulated or enhanced. The last step is mastering. Audio mastering is the process of preparing and transferring recorded audio from a source containing the final mix to a data storage device called a master recording, the source from which all copies will be produced (via methods such as pressing, duplication or replication). It's an important stage. Things can go wrong here. The mastering is the icing of the cake. It goes without saying that if the underlying recording has major flaws there's not much you can do in the mixing and mastering stages. Other than putting lipstick on the corpse. It doesn't matter whether or not you are a proficient and skilled mixing or mastering engineer. If you doubt me, listen to the original tracks and then to the added live track on these albums. Shit in, shit out. It's a vulgar restatement of "garbage in, garbage out". Vulgar, but nonetheless true.