is a fairly recent development in pop music.

Outside of jazz, and maybe folk, through the 1950s and early 1960s LPs were an afterthought to record labels: compilations of singles with some filler to capitalize on a singer's popularity.

It was only about 1965 and the following few years that things evolved so that
-albums could spawn singles, rather than the other way around, and
-pop albums could sell commercially in huge numbers to rival singles... I believe LPs only outsold 45s for the first time in 1968, though I'm not sure if that statistic is in $ figures or # of units.
-there was a radio market that played LPs (the emergence of FM, which John got into a bit)

While it's cliche, Bob Dylan's commercial breakthrough and the Beatles' 1965 run were extremely influential in the development of pop musicians' desire to make albums into cohesive artistic statements rather than collections of pop songs, and convinced labels to allow them to do so. Whether that was a good thing or not probably depends on the band/record/label.

Another thought on the importance of FM radio: since the sound was better than AM, I wonder if the fidelity available over the radio pushed bands & producers to better sonic standards? While a lot of us prefer a little grit or crunch, there's no denying that by the mid-70s studio recordings were of a cleanness unimaginable even 15years before.

To reiterate, tapes didn't change the landscape at all... in fact, it was frustrating to have 2 or 3 minutes of blank tape at the end of side 1 or 2 b/c the other side was longer.

CDs didn't start changing things until the early 1990s, when people started saying 'hey, we have 80 minutes available, we've gotta use it all' - to the point where fans would complain if an album was only 32 minutes. Again, whether that was a good thing is up for debate. Hidden tracks too. I don't think the evolution of skits as an important part of certain types of albums had anything to do with the CD format.

Now as far as digital, the long-term effect will continue to be the de-emphasis of the album. So the wayI look at it, the album was only about a 40-year period (say, 1965-2005) out of our 110 years or so of commercially recorded music.