Rules rules rules! Why are there so many rules in music theory and why should you obey them?

As a music theory teacher, this is a question I get asked a LOT. As well as things like, “did Bach ever break the rules?” or “why does this rule exist?” or “does this only matter for music theory exams?” and so on!

Today I got another email and since I gave quite a long answer to my student, I thought I’d write it up into a blog post too.

What are Music Theory Rules?

What we are doing is looking at the work of theorists who decided to describe the music being written by the most successful composers of any given particular age. The theorists analysed the music and encoded rules based on what they found.

For example, the 16th century composer Palestrina was considered by almost everyone in his day to write perfect counterpoint – non-theorists liked it because it sounded beautiful and pure to their ears. Theorists then dismantled Palestrina’s music, to discover how he achieved this. Then they wrote books on the contrapuntal style based on their findings.

Subsequent theorists read earlier works and took the rules as gospel, and over the centuries they have written more theoretical books – many agreeing with past books, many disagreeing and many offering up new ideas. That’s how music develops.

When you study Renaissance counterpoint, or trio sonatas, or four-part harmony in the style Bach, or whatever it is you are studying, you can either analyse the music yourself and deconstruct it to find the so-called rules, or you can read books by other people who have done the task for you (or both!)

But you have to remember that the composers themselves did not compose with a rule-book open in front of them. Music came first, and rules were devised later on the basis of what had been written.

So, yes, there are plenty of examples of composers breaking “rules”, and it is also true that nearly all the “great” composers (Bach, Mozart, Beethoven and more) studied the rule books in their youth. But all the “great” composers became great because they stretched the rules to their limits in their own lifetimes, and helped push musical style forward into a new era (Bach into Classical, Mozart into Romantic and Beethoven into Modern).

It’s also interesting to note that “rules” in music have become more relaxed (and so, fewer rules) as time goes by. In Medieval times, musical composition was ruled by the Catholic church, who had very strong ideas about what was, and what wasn’t “holy”. They originally only allowed perfect intervals in harmony (early Medieval) for example, because they considered all other intervals to be impure and therefore not fit for church. Ideas and fashions change, but they rarely change overnight, so Romantic composers would still have studied the same theoretical texts as composers hundreds of years before, but they would have felt less compelled to abide by the rules. Fast-forward to today, when living composers would find it ridiculous to abide by a rule book.

But, the rules still affect their work, whether they like it or not!

Because music in Western Europe has grown in this way, our cultural expectation of what will happen during a piece of music (whether it’s a symphony or rock song) is learnt from listening to the music around us, which still generally follows many of the old rules. We are used to the major/minor scale system, we are used to commonly occurring chord progressions. We are extremely good at predicting “what comes next” on the basis of all the music we have heard in our lives up to now, as this video demonstrates:

Things either sound “normal” to our ears, or they don’t. If you composed a piece of music which relied heavily on perfect 5ths today, it would not sound like an average 21st century composition. But you are certainly allowed to do it! Many modern composers (by modern, I mean from the 20th century onwards) deliberately broke the rules (as did their forebears). Debussy wrote consecutive everythings, for example.

Perhaps we should move away from the word “rule” in music theory. Really what we are dealing with is a set of instructions which will help you write in a particular style – nothing more.

Most music theory exams require you to apply the rules of a particular era – because if they didn’t, there would be no fair way to assess your work. When you write four-part harmony for example, you are expected to comply with the style of late Baroque/early Classical music. If you are writing species counterpoint, you need to comply with Renaissance rules. However, if you are composing new music for yourself or others to enjoy and play, you are categorically not obliged to follow any rules that you don’t personally agree with.

Go out there and experiment! Learn the rules, and then break them!