Why do EDM musicians often create an intro that is 15/30/45/60/120 seconds long?

Question

Not all tracks have intros, and usually those are extended mixes that have them (sometimes can be original mixes and remixes). However, I notice that often their intros are 15/30/45/60/120 seconds long, or taken in minutes these numbers are 1/4, 1/2, 3/4, 1, 2 minutes.

So, is there some kind of rule? Or is simply their inner OCD and these numbers are some kind of key numbers in music?

A few examples (links to beatport):

D.O.D - Glow (Extended Mix)

Lush & Simon - Callin' (Extended Mix)

Apster - Photobomb (Original Mix)

Swanky Tunes - Fire In Our Hearts feat. C. Todd Nielsen (Arston Remix)

For tracks that I looked their BPM was in 124-128 range, but I guess the actual range is wider than that. As you can note they are of slightly different genres and these were only 4 examples.

Answer 1

8 measures of a song in 4/4 at 128bpm, will take 15 seconds. Longer intros are multiples of this (16 measures => 30 seconds, 24 measure => 45 seconds, etc).

There aren't any rules per se, but there is a greater sense of completion when multiples of 4 or 8 are used for measures (as well as being a part of the genre).

Answer 2

When sequencers first came into use, the default tempo of a new song was generally q=120. So a whole LOT of music got produced at that speed. I mean, to change the tempo you'd have to look in the manual, and that's, like, heavy stuff man! (Music producers talked like that in the 80s.)

With 4 beats to the bar (another default setting) that made a bar clock out at 2 seconds, an 8-bar section at 16.

Now, if you'd said EDM sections were typically 16, 32, 48 or 64 seconds long, I'd have to wonder if exactly the same thing was happening!

(Where are these 15s, 30s etc. sections in the examples you posted?

Answer 3

To understand this question we have to combine what's been said by Laurence and nivlac.

1. The BPM of a typical EDM track

Will be around 120 bpm. This may be for historical reasons, as per Laurence's answer...

When sequencers first came into use, the default tempo of a new song was generally q=120. So a whole LOT of music got produced at that speed.

...but it's also true that 120 is in general a BPM at which is nice and natural to walk, move and dance! Exactly what people want to do when listening to EDM music. From this Quora question about why is 120 BPM such a common time signature:

[120 BMP is] also just a nice speed at which to get people moving quickly and with purpose. 120 bpm is standard American military march tempo [...]

And to back this statement up the Beat Explorer's Dance Music Guide comes to the rescue

Electro House usually sits somewhere between 125-135bpm and tracks are arranged in a way that gives a large focus on the climax or drop. This usually contains a heavy bassline, and frequently includes melodic elements to help establish cohesion within the track.

Which brings us to the second point:

2. The sense of completeness

Not only do multiples of 4 give us a sense of completeness, but having long intros and long tails makes it easy and predictable for DJ's to mix tracks on the fly, knowing when to switch from one track to the other.

Try it yourself: listen to a long EDM mix and count, you'll see that in most cases you'll be able to anticipate the drops, the cuepoints and the changes! Doing rationally so will give you a sense of accomplishment, which is the same amusement and accomplishment that gets people hyped when they dance to it.

Answer 4

So, is there some kind of rule? Or is simply their inner OCD and these numbers are some kind of key numbers in music?

You're kind of on the right track. I think it may have been said before, but the thing with EDM music is, repetition is key, but not for repetition's sake.

One of the more conventional things about pop music that carries over to (most, not all) EDM music is common time. Common time is defined as 4 beats in a measure. The number 4 here is then key for this.

Since EDM features the number 4 here a lot, that usually means musical phrases are likely in a multiple of 4. To explain a phrase, it's essentially a group of measures that "speak" completely. So, if a phrase is in multiples of 4, it can take 4, 8, 16, etc. measures for a phrase.

It's hard to think that in EDM music is in phrases, because oftentimes, the space at the intro of the track is filled with mostly a beat loop and sound effects, and maybe some introductory bass line that repeats over and over. However, the feel that pushes the music onward is this division of phrasing. You'll notice in these longer intros, new elements get introduced every new phrase. What might start with just a kick drum and some hi-hats may be joined by a snare or clap a phrase later, and then a bass line a phrase later, etc.

As far as how long it takes to "complete" an intro, it's relative. The length is usually destined by the bpm against the length of the phrase. A phrase consisting of 4 measures of 4 beats each, at a tempo (read, speed) of 120bpm (meaning, 2 beats a second) is 8 seconds. A phrase of 8 measures like this is 16 seconds, etc.

As far as history, there are two things here. One is what tempos were used for EDM. Modern EDM derives from a variety of styles of electronic music, but the general setting in many sequencers was 120bpm. It is always adjustable, and in the case of EDM, it's mostly around 120bpm-130bpm. Other styles closely related, such as Trance, ues higher bpms, as low as 128bpm to about as high as 156bpm. But, intros last as long as they do because they are buffer for a DJ to mix seamlessly from one track to the next. As the bpm of a track can be altered by how fast a vinyl is spinning, it is the necessary time for a DJ to find a suitable revolution speed on the table, adjust the vinyl until one track meshes well into the next, and align the phrasing between the two tracks, before panning the volume from one turntable to the next. This time is meant to link the outro of one track to the intro of another track, essentially making it so that the music doesn't stop and flows well.