And a One, And a Two...

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I was never much good at being a nerd. I've played Dungeons & Dragons exactly once, can't quote Star Trek scripts verbatim, and stopped reading superhero comics roundabout puberty.

But I can program computers a bit, I do read XKCD, and people often tell me I'm rude and insensitive - so that's something.

Today's nerdicule (defined as a particle of nerdery) came from a question: If I want to write a song of a particular target length, at a particular tempo, how many bars does that give me to play with - and by extension, how many verses, choruses, breaks etc. can I have, and how long can they be?

Well, the number of bars in a song is equal to the tempo in beats per minute, divided by the number of beats per minute, which is itself divided by the song length in minutes. In other words...

Bars per Song = Beats per Minute / (Beats per Bar / Minutes per Song)

There's usually four beats to the bar, so a three minute pop song at 120BPM gives...

Bars per Song = 120 / (4 / 3) = 90

But rather than work it out each time, how about a lookup table? The X axis is tempo, and Y is song length.

	2m	2m 30s	3m	3m 30s	4m	4m 30s	5m
80	40	50	60	70	80	90	100
85	43	53	64	74	85	96	106
90	45	56	68	79	90	101	113
95	48	59	71	83	95	107	119
100	50	63	75	88	100	113	125
105	53	66	79	92	105	118	131
110	55	69	83	96	110	124	138
115	58	72	86	101	115	129	144
120	60	75	90	105	120	135	150
125	63	78	94	109	125	141	156
135	68	84	101	118	135	152	169
140	70	88	105	123	140	158	175
145	73	91	109	127	145	163	181
150	75	94	113	131	150	169	188

The irony is, it took longer to work out how to make the table than to work out the equation.

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