In fact, the number three and its related proportions may seem almost magical. The Rule of Thirds has applications within many different fields:

From image composition (important objects are placed by dividing the total image into thirds), to diving (one third of a diver's oxygen is used during diving, another is used during the return, and the last third is kept as a safety reserve), to programming (a new class should be created whenever the same code is copied three times), to aviating (three miles of travel are allowed per each thousand feet of descent), to writing (things are funnier or more interesting in groups of three: Three little pigs, three ghost visits in Charles Dickens's A Christmas Carol, etc.).

There are several different ways of applying the Rule of Thirds within audio and music production. Let's start with the most well-known.

Microphone 3:1 Rule

When you want to use more than one microphone to record two sources that are in close proximity to one another, the 3:1 Rule says that you can minimize possible phase problems between them by ensuring that the second microphone M2 is distanced from the first source S1 at least three times as far as the first microphone M1 is distanced from source S1:

3 to 1 rule (mic to source)

Why does this work? According to the Inverse Square Law, the SPL of a sound source diminishes in proportion to the distance from that source (about 6dB each time the distance is doubled).

If M2 is three times as far from S1 as M1 is from S1, the level of the sound coming from S1, captured by M2, will be about 9.5dB lower than the level of the sound captured by M1, and thus any potential comb filtering will be much less severe, as the second wave won't have enough 'strength' to cancel out the first one.

You can find several online calculators here, which you can use to interactively change SPL levels and distances.

Inverse Square Law (source: Wikipedia)

Note, however, that this only applies if the gains of both microphones' preamps are similar. If they are not, the amplitude of the source S1, captured by the mic M2, won't be 9.5dB lower than the amplitude captured by M1.

In some texts, you'll see 3:1 Rule formulations that talk about the distance between 'the second and the first microphone', not 'the second microphone and the first source':

3 to 1 rule (mic to mic)

In the case illustrated by the above image, the rule under this different formulation would still apply, as the hypotenuse of the triangle shown is greater than 3R, and thus the second wave will still have significantly reduced energy. However, there are some cases in which stating the rule in this way could lead to possible problems:

3 to 1 rule (possible phase problem)

In this scenario, the wave coming from S1 captured at M2 wouldn't be 9.5dB lower than the wave captured at M1. There is an interesting debate about this issue here. In any case, and however you prefer to enounce the 3:1 Rule, when in doubt, just remember that the rule is based on the Inverse Square Law, and act accordingly.

Arrangements, Parts and Composition

In music, there is another way of using the number three. Whenever a musical pattern, idea or motif is going to be repeated for a third time, it's best to change it in some way, or present a new idea. This way, you'll surprise the listener (who would be expecting a repetition of the same pattern) and will thus maintain his or her interest in the song.

Let's take Mozart's “Serenade No. 13 for strings in G major” (Eine kleine Nachtmusik) as an example:

The piece starts at 0:02, presenting a musical idea (which lasts until 0:05). The idea is then repeated a second time, with some variation in the notes (from 0:06 to 0:09). Wouldn't it be strange, after this second repetition, to listen to the same motif again?

Instead, at 0:10 a new musical idea is presented. It is repeated a second time at 0:15. However, the ending of this second pattern changes, developing into a new idea at 0:17 that leads us into a small rest.

After the rest, yet another new musical idea is offered, at 0:22. It is repeated a second time at 0:30 but, again, not a third time. If you keep listening to the whole piece, you'll see how this technique is masterfully used to maintain your attention throughout.

Of course, this doesn't mean you should repeat everything twice and follow it with a change. However, it does suggest that when a motif has already been presented two consecutive times, it is wise to then change to a new musical idea (or to a variation of the previously presented musical concept) instead of offering a third identical repetition.

When a motif has already been presented two consecutive times, changing to a new musical idea will maintain the interest

This technique has been used for hundreds of years, but don't let this make you think it is something only used in classical music. Have a listen to any current song in the charts, and you'll probably find this concept within many of them.

However, in contemporary music, musical sections are usually less complex than those found in classical works, and motifs are repeated in longer fragments.

Also, a common variation on the rule of three is often used, in which musical ideas are repeated according to the following pattern: A B A' C. Usually, A and B are similar, and C represents a larger change. Let's listen, for example, to Pharrell's “Happy”:

The verse starts with a vocal melody, which is followed by an instrumental response (A). The second melody and instrumental response combination includes a small variation (B). The third vocal line (A') is similar to the first one, and the resolution comes with the fourth line (C).

The song could have followed this with a second verse similar to the first one (a second repetition), but in this case the chorus was introduced next, as it is the main hook of the song.

Here is another example, Lorde's "Royals", which uses the ABAC technique in the verses and the general 3:1 rule in the pre-choruses and choruses:

Bear in mind that this concept can be applied at different levels, from the 'micro' level (among parts of a small musical idea), to the level of bigger composite ideas (as in Pharrell's melodies within the verse), to the level of even bigger song sections (among the parts of an entire song's structure – for example: verse-chorus-verse-chorus-bridge).

Sounds, Samples, FX

Today's technology offers a lot of options and opportunities, and that's great, but sometimes you can find yourself facing too many alternatives.

You've probably been in the situation of looking for inspiration for, say, a new sound, and finding that you have at your disposal over 12 different great virtual instruments, each one loaded with hundreds – or thousands – of different sounds, patches, presets, etc. The same scenario might occur when you're looking for reverbs, delays, samples, etc.

Having so many options can be detrimental to your creative process. You can overcome this, again, by using a 3:1 rule: when looking for inspiration for any kind of sound, try limiting yourself to only three options.

Too many alternatives can be detrimental to your creative process

Take one of the pieces of hardware or plugins you have at your disposal, and browse its different posibilities. Once you find a sound you like, write it down (or save it), and then keep looking for other 'candidates' (using either the same or different equipment). Once you have three options that you like, stop there.

Instead of continuing to look for new sounds endlessly (you know that feeling: 'maybe the next one is even better'), try restricting yourself to those three alternatives. Now pretend that there are no more options available, and start working with your chosen three. Put them in context and modify their parameters, use other processors, apply new FX, etc.

After a while, you'll probably find that one of the candidates (or a combination of them) works best. Proclaim it the 'winner', and move on to another part of the production. Even if you are still not 100% satisfied with the results, try working on something else after a reasonable amount of time.

Moving on to another task will give you some healthy perspective, and when you later return to that sound or arrangement, you'll instantly know whether it works or not.

If it does work, mission accomplished. If it doesn't, just try one of the other two options you first chose. Or, look for three new candidates, and repeat the process.

The thing is, restricting yourself to only three alternatives will make you much more productive, as you'll be making decisions and committing to them more frequently. It is always better to have a great finished song than to have just a killer sound or idea that has been worked ad infinitum (and nothing else).

Recording and Comping

In the recording process, 'comping' is a very effective method of obtaining a great master take. For those who don't know this technique, in short, it consists of recording several different takes of the same part or instrument, and then choosing the best bits of each take, in order to create a 'composite' or master take.

This technique is typically employed when recording vocals, but it can be used when recording pretty much any instrument.

Comping example

However, if you record too many takes, you may find again that having too many options is counterproductive, as you may then have to listen to too many alternatives for each vocal line. This takes a lot of time, especially if several people are involved in the decision making process.

As stated in the previous point, it is usually better to restrict your options: if you plan on creating a comping later, aim during recording to produce three different 'very good' takes, rather than a bunch of 'regular' ones.

Once you have the three 'golden takes' ready, create a composite from them. The process will run much more efficiently, because when you are listening to only three options, it is much easier to remember each one and to choose the one that is most appropriate (easier than if, say, you had listened to seven options).

Once the comping is finished, if you feel there are some parts that could be better, just re-record those.

(Of course, the actual process may vary greatly, depending on the circumstances – the singer, available studio time, the production style, etc. but you get the idea)

Mixing

And, finally, here is one more way of introducing – and taking advantage of – the 3:1 concept in your workflow.

One risk when mixing is when you don't see the forest for the trees, and spend too much time working on isolated elements instead of focusing on the big picture.

Of course, you'll want to pay attention to both 'micro' and 'macro' levels of detail (following the forest analogy, a great mix will offer you an awesome 'forest' as well as many captivating individual trees), but changing from one perspective to the other may result difficult.

The good news is that switching between micro and macro modes is a skill that gets easier with practice. If you tend to dedicate too much time to isolated items, try this in your next mix:

Once you've done your preparation work and are ready to actually start mixing, take a countdown app and set it for three minutes. In the first stages of the mixing process, you'll dedicate only three minutes at a time to any one aspect.

Say you want to start with the drums. Activate the countdown, and commence working on them in whatever way you feel is needed (levels, eq, compression, etc.). Once the three minutes are up, switch to working on another element, maybe bass guitar.

Spend another three minutes on that element, then move to another, and so on.

Don't worry if you are not 100% satisfied with the sound you've obtained after the three minutes. This is a 'circular' approach, so you'll be able to come back later and spend three more minutes on it.

Forcing yourself to move from one element to another will prevent you from focusing too much on the details of any one element, which in turn allows you to have a broader and more comprehensive view of all of the instruments – and their interactions – sooner.

In the course of tweaking one element, you'll probably find that you need to readjust another one. That's fine: just take a mental (or actual) note, and focus a new 'three-minute set' on that element later.

Remember to also allocate 'sets' to listening to the whole mix, as well as to its different sections and transitions. Start the countdown, and spend three minutes working on the first chorus, three minutes on the first verse, three minutes on the transition from the second verse to the second chorus, three minutes on the bridge, etc.

Try this approach for a couple of hours, and you'll be amazed at how much more mature the mix is at that point (than it would have been if you had dedicated that same amount of time to working on only one or two instruments).