Why is a song's radio edit called a ‘7" version’?

Solution 1:

When I was growing up in the '60s, in Australia, there were three common formats of vinyl record available. My comments below are based on my own experience and purchases of records from major bands like The Beatles and The Rolling Stones.

1. Singles:

   • These were the primary format that was used to promote a new song from an artist. The tracks were commonly selected from a newly released, or about to be released, LP (A.K.A. Album).
   • The 'A' side had the song that was being promoted, and played on the radio. The 'B' side was not necessarily of less quality but was not promoted or played as often.
   • They were 7 inch diameter with one song per side.
   • They were played at 45 RPM.
   • Each song was usually about 3 minutes long, give or take 30 seconds. This seemed to be the preferred length for commercial radio stations.
   • This ties in with the the idea that the 7" version is the edit aimed at radio performance.

2. EPs (Extended Play)

   • These were also 7 inch, 45 RPM discs, but with two tracks per side.
   • Again they were usually a selection of tracks from an LP.
   • I think they were, primarily, a way for the record companies to get a higher value than singles for customers (young teens) who could not afford to buy LPs.

3. LPs (Long Play)

   • These were the major works of many artists.
   • They were 12 inch diameter and played at 33 1/3 RPM
   • Playing time was usually around 20 minutes per side.

Solution 2:

A "7 inch single" was a 7 inch diameter vinyl record, which ran at 45 rpm, with a single song on each side; the main 'A' side the 'B' side which normally had a less popular song.

Solution 3:

I think the point being missed in the otherwise good answers so far comes from a later distinction.

Yes, the 'seven inch' was the format of a 'pop single', potentially though not necessarily shortened from a longer album track - but until the 80's no-one would have called that single a 'seven inch', they would have just called it 'a single', as opposed to 'an EP' [Extended Play] 'an album' or earlier 'an LP' [Long Player].

The 7" distinction comes from when people first started making 12" singles - longer cuts intended for the dance floor. Often they would drop for minutes into deconstructed sections not really suitable for home listening & certainly not for mainstream radio. A 12" single would still be played at 45rpm unlike an album; the reasoning being that using all the available space for a 10 minute track as opposed to the 22 minutes of an album at 33rpm, you could space the grooves wider & therefore cut more bass into it.

So the distinction initially came about to differentiate the two physical formats & incidentally their intended audiences.

Later distinctions have come about as more & more different 'mix' versions of tracks became popular, hence the rise of the term 'radio edit' - as for the past few years vinyl formats haven't been so popular, so a lot of those simple 'distinctions by physical size' have been blurred.