@tzh21y, what titles are you referring to?
Music Matters uses stereo masters whenever possible. Their argument - as explained in the accompanying booklet - is that Rudy van Gelder was an early adopter and from late 1958 onwards recorded only in stereo. From then all mono mixes were 'folded' from a stereo master. The MM producers have a sonic preference for the stereo master tapes, possibly because the mono version involved one extra - potentially degrading - step in the process.
Apart from the mono/stereo question, these reissues are an entirely different listening experience than hearing the original pressings. RVG cut his lacquers very 'hot', which resulted in a highly visceral, punchy presentation. This effect is even more pronounced on the 'folded' mono's, which is perhaps the reason why many collectors prefer them. The Music Matters are cut far less 'hot', resulting in a more 'civilised' sonic presentation. I've never played these stereo records in mono, but will definitely try. Perhaps it restores some of the dynamic punch of the originals that is lacking in these reissues.
BTW like most engineers it took RVG some time to get to grips with stereo recording and some of the early ones have an extremely 'panned' left/right channel separation with a huge hole in the middle. Perhaps the 'weird resonance' you notice was another problem from this early stage. But even stranger things could happen, like hearing Blakey's growls on one channel, while his drum kit is on the other! Of course in such cases the mono version is much preferred (or switching your amp to mono).
@syntax, the MM reissues claim to be 100% analog, with access to the original BN master tapes. The pictures in the booklet suggest as much, but my guess is as good as yours.
