Let’s learn about perfect 5ths!
Perfect 5ths are one of the most commonly used sounds in all of music history, yet we never seem to talk about them outside of music theory. I'd like to help with that, because knowing about perfect 5ths can boost your piano power in a serious way! ✨🎹✨
Today I show how you can easily learn to find and use perfect 5ths, even if you have no knowledge of music theory. Hopefully by the end of this video, you'll love perfect 5ths as much as I do!
What is a perfect 5th?
A perfect 5th is a combination of two notes that are five letter names apart, as they are found in the lower note’s key signature. For example,
A perfect 5th up from C is G
A perfect 5th up from E is B
Which key signature should you use to determine a perfect 5th? Whichever one is easier for you to remember! Composers realized long ago that the 5th is the same note in both the major and minor keys. That’s why they called the 5th “perfect” rather than major or minor — they thought it was a really special quality of music and it didn’t make sense to label it as one or the other.
For example, most people find it easier to remember the C major key signature (no sharps or flats) than C minor (three flats). So if you wanted to find the perfect 5th up from C, you’d probably use C major as your guide. But most people also usually find the E minor key signature (one sharp) to be easier to remember than E major (4 sharps). So if you wanted to find the perfect 5th up from E, you’d probably use E minor.
Some books and teachers also explain that a perfect 5th is seven semitones apart, but I don’t really like teaching it this way. The number of semitones doesn’t have anything to do with the perfect 5th. Perfect 5ths are determined by their key signature. Teaching it by semitones is technically accurate, but doesn’t give the student greater understanding.
How do we find a perfect 5th?
There are two ways I recommend finding perfect 5ths. One is by determining it based on the key signature (requiring knowledge of theory), and the other is determining it based on sight (more helpful for people trying to spontaneously play at their piano). Let’s dig in!
Determining a perfect 5th by using a key signature:
Start with any note on the piano, and decide which key signature (major or minor) you know best for that note. Count up four more notes until you have spanned a distance of five letter names in total. Check the top note to see if is affected by the key signature. If so, add the sharp or flat as needed!
Example:
A perfect 5th up from G is D.
A perfect 5th up from B is F sharp.
A perfect 5th up from E flat is B flat.
Determining a perfect 5th without using a key signature
Back when I was learning piano and didn’t understand music theory yet, I realized that you can also find a perfect 5th simply based on its location on the piano. Here’s what I noticed:
Most perfect 5ths that start on a white note end on a white note, and most perfect 5ths that start on a black key end on a black key. For example,
C-G, D-A, and E-B are all examples of perfect 5ths that start and end on white keys.
D flat-A flat, E flat-B flat, and F sharp to C sharp are all perfect 5ths that start and end on black keys.
The only exceptions to this rule are perfect 5ths that start on the notes B and B flat.
B is a white key whose perfect 5th is a black key (F sharp)
B flat is a black key whose perfect 5th is a white key (F)
This can all be summarized in one rule:
A perfect 5th will always be a white key to a white key or a black key to a black key, EXCEPT for perfect 5ths starting on B and B flat.
This can make it very easy to find perfect 5ths by sight or by ear. If you can count up the keys really quickly, or remember how the distance of a 5th feels under your hand, you can actually guess and aim at a perfect 5th pretty accurately! This is how I played perfect 5ths for years until I learned and understood music theory so well that it became more natural for me to find perfect 5ths based on key signature.
How does knowing about perfect 5ths help us play piano better?
It’s really common for beginner players (and their teachers!) to focus on note names and key signatures, but perfect 5ths are so foundational to music that their value goes beyond just knowing music theory. Learning about perfect 5ths can help you become familiar with your piano much more quickly and open a whole world of playing to you before you even learn music theory!
Here are a few examples of what I mean:
Figure out more accompaniment patterns. In the past, I’ve shown my favourite rhythm pattern for beginners, which uses a basic left hand octave to accompany a right hand chord. If you know how to find a perfect 5th, you can expand beyond a basic octave and start adding the perfect 5th to the middle of your left hand. I call this a I-V-I pattern, which is shorthand for playing one note, its perfect 5th, and repeating the first note one octave higher. This is probably best understood by watching the video. My I-V-I demo starts here.
Find chords more easily. Now that you know how to find perfect 5ths, you’re halfway to knowing how to find major chords! A major chord is a perfect 5th with a major 3rd in the middle. If you take what you’ve just learned about perfect 5ths and combine it with what I shared in a previous post about major 3rds, you have an easy way to find any major chord on the piano, before you’ve learned any music theory! Knowing how to find major chords on the piano is a great first step to playing music independently. Combine that with my favourite rhythm pattern for beginners, and you can add hundreds of songs to your practice right away!
What do you think of perfect 5ths?
Perfect 5ths are one of the most foundational sounds in the history of music. Understanding how to find them is a big step towards piano independence!
Did this post help you understand perfect 5ths better? How do you see yourself using perfect 5ths in your own playing? I’d love to hear your ideas. Please feel free to leave a comment on this video and let our learning community know what you’re up to!
Have fun!