One of the many good things about newer digital media formats and the devices that store them is the fact that they're easy to back up and therefore preserve. That's definitely a major strength compared to the older analog format that stored things like old movies, old TV shows, and old audio recordings. In fact there are a lot of the oldest audio recordings on records and magnetic tapes, that have been so tortured by the passage of time that, for the most part, they're torture to listen to. These are the recordings of someone playing blue grass back in the nineteen twenties or thirties that have a sound of the voice trembling, and you assume that the singer actually sang that way and you wonder why anyone would sing that way on purpose and who would want to listen to it, let alone actually go to the trouble of recording that awful sound. Actually, it's not any defect or intentional modulation of the singer's voice. In reality, those trembles in the music are defects that have accumulated on the acetate or vinyl record or on the actual magnetic tape that the recording inhabited all of those years and decades.
There are a number of things that contribute to the degradation of these types of recordings. The first is simply the passage of time. Over the years, the vinyl that records are made out of and the celluloid that the magnetic tapes are made out of both out gas volatile organic compounds. In other words, these materials simply dry out. This causes them to be more brittle and may even contribute to them changing shape enough to distort the recordings that are encoded on them. Moisture can also cause problems and in the case of many of those blue grass recordings that were made and have been stored in the humidity of the southeast, that's a realistic problem. Of course, protecting the tapes and records from moisture is possible by storing them in a climate controlled environment, or keeping them cool and away from sunlight like in a freezer or a refrigerator would probably do the job, but no one has taken that kind of care to preserve these recordings.
The other kind of degradation that these recordings are subject to come from actually playing them. For example, the needles on record players gradually wear away the vinyl of the records. With magnetic tapes, all of the pulleys that are part of the tape players can pull and stretch the tape. Both of those things can seriously distort the sound quality.
Now there's special software technology that can allow these recordings to be remastered digitally while eliminating a lot of the distortions that have accumulated from their long storage in analog form and the wear and tear they've been subjected to. This technology recreates a virtual version of the original recording device. Then when the beat up old recording is fed through the program, the program can use the virtual model to eliminate the errors. The result is a much improved version of the recording where the music sounds like what someone would actually want to create intentionally.