But I found always reassuring the possibility of keeping a pure form of data that can reconstruct a WAVE, as if it was a MASTER TAPE, than depending of just analog recordings of various qualities.
I'm not an OpenMSX user and don't really care much about if it supports TSX or not, but isn't this something you absolutely want to avoid from a preservation standpoint?
If you have a tape you want to record the analog signal and preserve it that way as the master.
Whatever method you use to generate a clean stream from that noisy data may or may not generate bit errors, but as long as you keep the WAV data around you can always redo the conversion with a different method.
A cleaned up format could be convenient for emulators so that they don't have to decode the "analog" stream, but it seems to me that anyone using it as a data preservation tool is doing more harm than good.
Recording the analog signal is not necessarily good. First, that was something originally digital, that was converted to analog, recorded as a analog. Then you are reading it back, analog, but converting it to digital to save in a computer in wav or other format. There are several factors that make this not optimal, including the quality of the conversion, the sample rate, the chances of not getting a transition in your sample rate properly enough, one thing is to make it sound similar enough to our brain Tha is always transforming whatever we see and hear, the other is picking up proper transitions so the signal is understood... How large should be a sample rate to guarantee it is really faithful, not to our ears, but to the systems the end audio is intended for? TSX is not a faithful copy of the analog audio, but, a faithful copy of the master that created the audio that went into tape, for preservation purposes, that is second only to the original digital memory dump 
TSX is not a faithful copy of the analog audio, but, a faithful copy of the master that created the audio that went into tape, for preservation purposes, that is second only to the original digital memory dump
Unless I have missed some features of TSX that just doesn't make sense.
To be sure that you have a clean recording you will then need to obtain a real master binary from the content creator.
If you have clean data to begin with either format works fine, you can just set a samplerate of 4800 and generate a square wave at full amplitude.
The problem is when you don't have the original binary, just a tape or a recording of it.
From what I have seen you can't convert it to TSX without starting to make decisions of what the bits actually are.
Either way you are removing all the information that could be used to verify that the conversion was correct.
That is absolutely terrible from a data preservation standpoint!
So unless TSX have some way to store the analog format it seems to me that it is best for data that has never touched a tape to begin with.
There may be arguments to use TSX, but unless I have completely misunderstood what the format does, data preservation isn't a reason to use it.
