The room left over

An album's length, the break between its sides and the number of songs on it have always looked suspiciously like the format it was sold on. Two sides of about twenty minutes in the vinyl era; something closer to an hour once the compact disc arrived. That invites a question in two directions. Did the medium make the album, or did the album, or something like it, make the medium?

The record supports neither answer on its own. The long-playing record was indeed sized to hold existing music, but not the music that made it famous. The compact disc's famous origin story, in which a symphony set its length, is the manufacturer's legend and is disputed by an engineer who worked on it. What the album became, in both eras, was mostly a matter of filling whatever room the format happened to leave.

Timed for symphonies

Edward Wallerstein became president of Columbia Records in 1939 and pushed its engineers toward a longer-playing disc. In an account he recorded with Ward Botsford, published by High Fidelity in 1976, he described rejecting prototypes that played seven or eight minutes, and then ten or twelve, as "not a long-playing record." Asked by CBS's chief, William Paley, what a long-playing record was, he "timed I don't know how many works in the classical repertory and came up with a figure of seventeen minutes to a side. This would enable about 90% of all classical music to be put on two sides of a record."¹ A 78 rpm side, he noted, had broken movements into pieces of about four minutes twenty seconds.¹

So the LP's capacity was set by an existing body of work, measured with a stopwatch. It is a clean case of content shaping the medium, though it comes from the man who made the decision, recorded long afterward, which should temper how exactly its numbers are taken.¹

What follows in his account is the more revealing part. "Up to now our thinking had been geared completely to the classical market rather than to the two- or three-minute pop disc market," he said. Columbia launched the LP anyway, without a matching record for popular music, "and in consequence lost the pops market to the RCA 45s."¹ The format was built for symphonies. The kind of record it is now remembered for, the pop album of ten or so songs in two sequenced halves, grew up inside a container designed for something else.

Once pop musicians were working in that container, its dimensions shaped what they made. In a 2026 analysis of 2,284 studio albums released between 1953 and 2026, a mix of critically acclaimed records and each year's biggest sellers in the US and UK, Mitchell Stirling found that vinyl albums "worked best at around 20 minutes per side, 40 minutes overall."² Before 1983, his average album came in just shy of 40 minutes.² A side is not only a time limit but a structure: it ends, the record is turned, and a second opening follows. The habit of thinking in halves, with an opener and a closer for each side, comes from the medium, not from any intention of the people who timed it for the classical repertory.

The legend of the Ninth

The compact disc has its own story of content shaping a format. In the official history Philips published, as quoted by the engineer Kees Immink, "the playing time was determined posthumously by Beethoven". In that version, the wife of Sony's Norio Ohga wanted the Ninth Symphony, her favourite piece, to fit on one disc, and the longest known performance, Wilhelm Furtwängler's 1951 recording at Bayreuth, ran 74 minutes, which became the disc's maximum.³

Immink, who worked on the format at Philips Research, does not believe it. In a 1998 account he wrote that the diameter was decided by Philips's senior management, who said the Compact Cassette had been a great success and that the CD should not be much larger; the final disc came out half a centimetre larger than first planned, at 12 cm. Of the stories connecting it to Beethoven, he wrote: "you should not believe them."⁴ In a 2007 essay he added that the minutes of the meetings give no clue why the playing time and diameter changed, and offered a commercial guess. Philips's subsidiary Polygram already had a plant in Hanover set up to press smaller discs, and a larger format removed that head start.³ He is careful to say the decision was taken outside the group of experts and that he can only guess.³

Neither account settles it. One is a company's history of its own product, the other the recollection of an engineer from the same company, and both have reasons to tell the story the way they do. But the contest is itself instructive. The version in which a symphony determined the format is the one a manufacturer would choose to tell, because it makes a commercial standard sound like a service to music.

Filling the room

Whatever set the CD's capacity, albums expanded into it. Stirling's sample went from just under 40 minutes before 1983 to 55 minutes by the 1990s. "Most of that growth came from more songs in the tracklisting and not by longer songs," he writes; the average number of songs rose from 10 to 13.² His sample is selected rather than random.² A rise that coincides with a format is not proof the format caused it. Still, it is the strongest evidence here of the medium changing the album, and it worked in the simplest way: once there was room, the room was used.

Nobody in this record designed the CD for 13-song albums, any more than Wallerstein designed the LP for pop. The capacity came first, for reasons of repertoire, packaging or competition, and the album took its shape from what was left over. Streaming then removed the container altogether, which means an album's length is no longer set by how much a disc can hold but by how plays are counted and paid for, a different mechanism with a different history.