Musicians and listeners alike will care, at least to some extent, about how long a song is. Like how we collect information about objects with simple definitions like "what color is it" or "how big is it", a song can be defined by things like "how fast is it" and "how long is it". The one we'll talk about here is "how long is it".
Yes, the one important question in this article is, "how long is it?" This might seem like the kind of question a 5-year-old would ask, but it's actually very important for anyone from the most casual listener to the most advanced musician.
But why is it so important? Few people associate a tune with its length in minutes and seconds, even though computer programs, CDs, and other devices constantly tell us how long a song is and how far we're through it while we are playing it.
The importance is as much subconscious as it is conscious. People don't assume a song is bad if it's 10 minutes long, or only a minute long. This could be considered a good thing or it could be considered a bad thing, depending on the way you look at it.
It's not necessarily a good thing because the length of a tune is important. And it's not necessarily a bad thing because knowing that a specific recording is 1 minute and 24 seconds long is not particularly useful information.
The importance of all this information is that people, especially these days, have limited attention spans. Gone are the days when 6 minutes of music required a large disc and a large music player with a high overall cost, when people felt privileged to have any music records of their own at all. People are no longer panting for music records; thousands and thousands are on YouTube and similar websites and applications, accessible for no additional charge and offering hundreds of hours more music than any compact disc or other kind of disc could offer. Therefore, people now can pick and choose how much music they want to listen to and which music they will listen to, and therefore they are no longer so grateful for having the music.
The response is that musicians must cater more to their audiences. Time has shown that 3-4 minutes is the best length for one recording. It's long enough to be worth a listen, yet at the same time does not bore casual listeners. Yet improvisation in jazz has always captured large portions of the clock.
The last part of jazz history when musicians did not squander recording time was in the late 1940s and early 1950s when there was an approximately 3-minute limit on each recording caused by the comparatively primitive recording technology of the times. For example, Charlie Parker's bands often included several musicians, and for most of the musicians or all of them to solo on a recording, each solo would have to be far below the ideal length. Naturally, any genres where musicians don't improvise rarely have to worry about keeping recordings under about 3 minutes; in fact, they're more likely to struggle reaching three minutes of recording time than going over it.
The problem is that the long-playing records in the mid-1950s and onward for all practical purposes removed the limits on recording time; each musician could now solo as long as he liked. Compared to all the interesting variations of the 3-minute Parker recordings, these newer recordings had long stretches that sounded fairly similar unless you listened closely to what each soloist was doing.
The length of jazz recordings of the mid-1950s didn't help anyone. While there were some long jazz tunes that were hits, there were not as many as there perhaps could have been. Playing tunes many times, not having solos of different lengths depending on the instrument and the performer, and having everyone solo on every tune (with the exception of the bass and drums, and sometimes the piano) resulted in recordings that could easily have bored people before the recording was halfway over.
Meanwhile, pop recordings have throughout history stuck to the "singles" that are short and, therefore, easier to remember and follow. If a piece of music is intended to become popular, it can't be 25-minutes of complex chords. It must be fairly short, memorable, and to the point.
Will be continued