As has been discussed here several times, in many cases the mid-50's 2-track stereo duped reel tapes 
sound and also hold up better than later 1/4-track stereo tapes. In most cases, these were 
small-quantity and premium-priced products, so a certain amount of care and quality control were 
taken. In the early days, record companies did their own duping or out-sourced to a known entity 
such as a larger studio operation. There were one or two indepedent tape-dubber operations dating 
back to the early 50's, Leon Wortman wrote an article about his in an early 50's issue of Radio & TV 
News. In fact, Ampex apparently read that article carefully because a lot of the hand-built features 
of Wortman's dubber chain were included in the Ampex 3200 system that came out in the mid-50's. This 
was then the standard dubbing rig in the US throughout the 2-track era.

I can't speak to how other companies did this, but know a few facts about Mercury's operations. The 
duplicator master was a 15IPS copy of the 3-2 "mixdown master" made at the LP cutting session, so 
the dupes were fourth-generation tapes. They were duped at 4x speed (60IPS for the dupe master and 
30IPS for the slaves). The duping took place at one of Mercury's pressing plants, probably in the 
midwest. Distribution was through the same channels as the top-line new-release records, for 
instance not in supermarket or dime-store racks. The tapes carried a premium price and the early 
ones held less content than the LP records. But, in 1956-57, this was the only way a home listener 
could experience 2-channel stereo.

In the very early days of duped stereo tapes (1954-55), before most of the major record companies 
got into it, there was a small "format war" between Magnecord-style staggered heads and Ampex-style 
"stacked" in-line heads. Once Ampex got heavily into the duping equipment business, and the 
home-playback business, this went away and in-line heads prevailed.

After the stereo LP came out in 1958, Ampex improved their technology so they could mass-produce 
1/4-track heads in the price range for home-playback gear, and also created duplicator heads that 
could handle the narrow track and the high-frequency content of a high-speed dupe. Everyone 
recognized the economy of half the tape stock and half the duping time, and the bone for consumers 
was fitting both sides of any-length LP onto a single reel. Thus 2-track was doomed as a consumer 
format. We've discussed numerous times all the disadvantages to duped 1/4-track tapes, and many old 
tapes are plagued with edge-warp meaning you have left-channel dropouts on top of hissy, 
often-distorted sound. The duper speeds kept increasing through the 60's, which made for even worse 
sonic quality. Late-60's 3.75IPS tapes were duped at 16x, and I've never come across one that sounds 
halfway decent. Another trend in the 60s was big duping operations like Ampex and Bel Canto and GRT 
becoming the outsource factories for the major labels, with lower quality control and cheapo tape 
and reels employed as time went on. Bel Canto Mercury tapes are particularly bad, often with the 
channels reversed and bad level differences between the channels. Mercury must have been sending 4th 
or 5th generation tapes out to be duped, because the hiss level is insane on some of those tapes. 
These kinds of decisions were made by the busines folks, not the music folks.

In the 70's, reel duping seems to have undergone a short renaissance. Quad reels I've transferred 
were made on lower-noise tape stock, and generally are dynamic and low-hiss, and track well as far 
as azimuth goes. Dolby B encoding was employed in some Quad tapes, lowering hiss further. Again, 
reels of this type that I've transferred tracked the Dolby B decoding well and sounded quite 
dynamic. You also had operations like Barclay Crocker doing a better-quality duping and charging a 
premium price. Barclay, despite the text in their reels, was definitely not getting access to 
Mercury master tapes (I don't know what their situation was with other labels), but their dupes were 
superior to earlier-era 1/4-track reels.

In my opinion, there is a cultish attraction to the early 2-tracks with some exceptions. Material of 
high musical quality that wasn't released on CD or that the CD was poorly mastered or not made from 
the original master tape may sound better than the mass-market product currently available. But 
these are the exceptions, especially vis-a-vis the Mercury, RCA and Columbia reel catalogs. Almost 
all of the material in those catalogs originally issued on 2-track tapes has been reissued on CD (or 
SACD) with a good-quality remastering job. I'm speaking only of classical, pop and jazz are 
different matters. Part of the pricing has to do with who's interested -- generally people with the 
means to be customers of the Tape Project and other premium-priced content operations. But I can't 
imagine anything but disappointment at most of these tapes after you've gotten used to a modern 
15IPS tape that is allegedly only 2 generations removed from the master. Believe me, the old 
2-tracks aren't anywhere in that league of quality. Tape-generation loss, noisy old tape stock, the 
inferior quality of high-speed duping and the ravages of time assure that to be fact.

-- Tom Fine