I have a huge music library that is a mix of true stereo, rechanneled/fake stereo, true mono but on 2 channels, and mono on 1 channel.
MC has a standard field that states the number of audio channels that exist in a recording: 2 or 1. Normally, MC plays a 1-channel recording as if it is 2 identical channels.
Of course, a true 2 channel recording might be true or rechanneled stereo, or mono with 2 identical tracks.
To identify the nature of 2 channel recordings, I have a custom field that let's me mark each track's audio format: S or M or R. In some cases I have the same song/performance in all 3 format.
Note that a 2-channel mono track might not truly be identical tracks, depending on the source and how it was digitized. A seeming-mono recording on a CD might not have absolutely identical tracks, depending on the source recording and variations in the audio chain.
Photograph records (aka vinyl) can be much more complex. For instance, playing a mono record on a stereo turntable will usually result in slight differences between the tracks. This is partially because a stereo photo cartridge senses both vertical and horizontal movement, while a true mono pressing puts all its information in the horizontal motion, so stylus vertical motion is spurious, random, and just noise. It's another discussion about how to improve this, but one key is to bridge left and right together, which tends to cancel out the noise contributed by vertical stylus motion.
Rechanneled/fake stereo can be difficult or impossible to convert back to reasonable-sounding mono -- whether via a software button or cabling or whatever. The problem is that the effort to make the mono source have different left and right channels (rechanneled into stereo) often includes separating various frequencies, introducing reverb or other tiny delays, and altering audio phase. These tricks can create a bit of spaciousness when the rechanneled audio is fed to speakers, though the tricks often don't work for headphones. But the problem is that the left and right audio is the same only different -- different enough that pushing it back together can yield some really, really bad sound -- distortion, bizarre frequency balance, odd echo, even "purple haze" sound. The result is almost never acceptable.
Most rechanneled/fake stereo recordings are performances that were not actually recorded in stereo/multi-track. The fake stereo versions were created so record companies could publish vinyl LPs branded as STEREO so customers would buy them. Once people bought stereo systems, they wanted to buy only "stereo" albums, whether fake or not.
It took a long, long time for stereo to become universal in recording studios. And even longer for the recording industry to mostly ditch fake stereo. But it's not entirely gone. By the time CDs came along, most such recordings were switched back to clean mono. But not all, unfortunately. And oddly, sometimes CDs have mono of recordings that were originally made in stereo, but someone either "lost" the stereo tapes or didn't care enough to dig them out. The Byrds Mr. Tambourine Man is an example -- published in mono or fake stereo for almost 40 years, then suddenly the stereo version popped up. Same with The Beach Boys California Girls. And witness the recent release of stereo CDs of all the Beatles songs that were originally done in stereo (most of them). For almost 30 years, several Beatles CDs were published only in mono, even though the original vinyl albums were published in stereo. (And don't even ask about Rolling Stones recordings...)
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Topic: Feature request: Mono/stereo button and/or tag (Read 2819 times)