There have been some interesting discussions on music recently. Jantango, who is close to the source, got an answer to the three-minute question recently.
So is a tango three minutes because records lasted only three minutes?
Well, records never needed to last three minutes. They could have been bigger or smaller, they could have revolved faster or slower. In fact it looks as if they were designed to record three-minute songs. It was a convenient length, it was the length people wanted, and still like. My memory of English folk songs is pretty distant, but it wouldn't surprise me if they are three minutes long, mas o menos. Perhaps the precursors of recorded tango lasted about three minutes too.
What do we get in three minutes? Most tangos, and most songs generally, are A-B-A in structure. It's a structure people seem to like, it works well musically and in a song. 16-bar blues follow much the same pattern. In practice, we get three segments of around 16 bars each. 16 bars to a minute, mas o menos, 48 bars start to finish. 48 bars of four beats each, that's 192 beats in three minutes, which is... 64 beats a minute. A familiar number. 192 heart beats to a tango.
& some hard evidence: I've got the piano version of Sur here, 'Letra de H. MANZI, Musica de ANIBAL TROILO'. It's in two pages: A and B. There are three verses, corresponding to A-B-A. A has 17 bars, B has 18 bars.
Jantango writes that Julián Peralta, who teaches at the National Tango Academy in Buenos Aires, was a member of Orquesta Tipica Fernando Fierro and is presently with Orquesta Astillero, gave this answer to the three-minute question: '...a tango is a synopsis rather than a novel. It says what is necessary musically and sometimes with words, in a couple of minutes. It is complete with theme and variation.' Which I really like. He says that it gives us everything we need. & if we need more, well, we just play three or four of them, one after the other! What would a milonga be like if each tango went on for 12 minutes?