'Loudness', the music industry and vinyl: a happy accident?

In my experience, I've not heard of compression used in jukeboxes.In the 50's, jukeboxes started coming with AVC(automatic volume control) with it's purpose to prevent sound blasting from the jukebox at the beginning of a record. The jukebox is set at a certain base volume level, and we know that not all records are cut the same, so, at the beginning of a record, volume would start at a reduced level and then brought up to level slowly in case the records started hot. Volume was consistent through the rest of the record with the AVC dropped out. In the transistorized jukebox amps of the 70's and beyond, some had 'scratch filters'. Nothing special, it was putting the treble level at a constant. I never use it as it tends to muddy the sound.
With the "Hey Jude" single, because it was so long, levels had to be kept low because the groove spacing was so close that they didn't want one groove running into another. It was helpful that it was a mono recording. Yes, it was cut like the old EP's.
Even longer, at 7:55, LZ's "Stairway To Heaven" was a much more troublesome 45 to make, especially since it was stereo on one side and mono on the other. These were never commercially release in the U.S. but were only sent to radio stations. All the copies that I have or have seen were pressed by SRC on vinyl rather than Atlantics usual styrene. Small grooves didn't work well on styrene.

 

DR value is defined as "the average cumulative difference between peak and loudness (RMS) over a specific period of time". DR value is not the actual "dynamic range" of a waveform, which should be calculated as ratio between the largest and smallest values of it. DR value is close to what is known as crest factor, that is the peak amplitude of the waveform divided by the RMS value of the waveform. RMS value, defined as the square root of the arithmetic mean of the squares of the values of the waveforms, is proportional to the peak amplitude of the waveform: so if you change the replaygain of an audio file you'll change the peak amplitude of the waveform, and the RMS value will be changed proportionally. The crest factor will remain unvaried and approximately the same applies to DR values.
Just do a simple test: choose an album in your collection, calculate its cumulative DR value, then do the same after decreasing all the tracks by 1 dB, then 2 dB, then 3dB... then compare the DR values. For a quick example, check the two editions of "Greatest Hits" by Rod Stewart: the repress is 2.6 dB quieter than the original "target" issue, the DR value is the same.
Album details - Dynamic Range Database
Album details - Dynamic Range Database

Apologies for derailing the thread. Let's get back on topic now.

 

Remember that the digital we listen to on CD as a standard is based on 1983 technology - that 16 bit PCM is the best they could do, and is "adequate" - there is really no reason the "standard" couldn't be 24 bit, which would increase sound quality a great deal - at this point just putting 24 bit chips in devices wouldn't even cost any more.

We were luck vinyl sounded as good as it did - it's really more of a fluke.

Every other music format, cassette, 8-track even reel-to-reel, features some pretty poor sound quality. Because most people are just as happy to hear their favorite song coming out of a $15 clock-radio.

 

In what area would sound quality be improved?

I've been reading up on the coarsegroove era. It took ~50 years of experimenting and incremental developments to arrive at microgroove technology. I think calling it a "fluke" is oversimplifying the matter.