For albums released in 1967 and especially in 1968, the mono is worth more, sometimes much more than the stereo. Mono albums, on the other hand, are being mastered from tapes that have remained virtually intact for almost 50 years. The resulting editions usually sound as good, or even better, than the original versions. In addition, in many cases, they are much more affordable, since some of the hardest-to-find monopresses of the late 1960s sell for hundreds or even thousands of dollars on the collector market.
Mono discs are considered older than stereo discs. Having an older mono album is rare, and they are more in demand because artists and bands initially recorded older songs with mono audio. Therefore, they sound better in a monkey. Speaking of jazz, jazzbos tend to believe that the monkey is better no matter what.
The original 1950s and early 60s editions of anything from Blue Note, Prestige, Riverside, Impulse and Columbia are more valuable. And it's true that these mono records tend to sound better. To my ears, they can sound louder, with instrumentation that sounds clearer and, at best, the sound may seem to be coming from the speakers. But how much better are they? I know I used to try to avoid stereo releases of jazz records from the mid-'60s and earlier.
I was under the impression that they were a “fake stereo” created in dimly lit back rooms to get on the stereo bandwagon. When stereo was still new, many record labels released “stereo demo discs” filled with vocals, orchestra sounds, and even street sounds to get buyers excited about the new format. Record companies make money by selling both new releases and titles that are already available, known as the “old catalog”. This was problematic for buyers, since few stereo discs had a prominent label in relation to the actual nature of the disc's content.
As for qualitative hearing differences, the mono versions tend to sound more direct and have more strength, since instruments tend to “compete for space and overlap”. On the other hand, stereo discs should not be played on a mono record player, since a mono cartridge doesn't move both sideways and vertically, damaging the slots on a stereo LP. Although these recordings weren't really stereo, they were packaged as stereo discs, often with a small note on the cover stating that the music had been artificially enhanced to simulate stereo sound. Since the stereo versions of many of these albums have been available and printed continuously for decades, stereo master tapes are often in poor condition, leading to stereo discs being released today that don't sound as good as when they were first released.
You can distinguish each instrument more clearly, but they don't combine to make them sound as powerful as in mono. The audio reproduction of mono vinyl records revolves around sounds, which produces a more impressive effect, since all the musical parts compete for the same space. They were usually albums that featured all kinds of sounds: vocals, orchestras, locomotives, jet planes and more, all recorded with deep and spacious stereo sound. The process varied, but in most cases the engineers divided the mono recording of the master tape into two signals.
For record companies, that meant buying stereo recorders, then expensive, to record their music in stereo. Of course, panning instruments or adding stereo reverb will make the sound of a recording different from that of a mono version. .