Liam Ward
- Oct 25, 2022
- 6 min read

How to Find the Key of a Song | Beginner Harmonica Lesson

Hello! In today's harmonica lesson I'll give you my top tips for figuring out the key of a song.

All musicians need to know what key a song is in, but harmonica players especially need to know so we can pick up the right harmonica for the key of the song. Otherwise it can lead to some pretty horrible sounding music!

If you want to know which harmonica to pick up for which key, check out this lesson.

If you want to learn about positions, check out this beginner's guide to positions.

What is a key?

Let's start with a question: what does it mean for something to be in a certain key? The key, or tonic, of a song feels like the safe space, resolution, or "centre" of the song.

For example, play a C scale on your C harmonica:

4 -4 5 -5 6 -6 -7 7

When you reach the seven blow, it sounds like home. It sounds like the natural ending to the scale. If you miss off the last note, the scale doesn't sound right: it sounds tense, like it still needs to go somewhere else. This is because is needs resolution. Add the last note in again and it feels like a relief, like the tension has been resolved. So, the C note is the tonal centre of that scale.

Almost every song has a tonal centre - a note which feels like the safest and most natural note to play and return to.

Knowing the key of a song is useful because it helps you to understand which chords and notes the song is based on, but most importantly for harmonica players it allows you to find the right harmonica!

The most common keys

Any style of music can be played in any key, but as a quick rule of thumb:

Most blues music will be played in the keys of A, E, G or C.

Most country music will be played in G, C, A or D.

Most rock music will be played in E, A, G or D.

There's no shame in asking what key the band is playing in. In fact, it's a necessary question to undestand what you need to play. However, it's not always practical to ask. Perhaps you don't have time at a jam or open mic, or you're listening to a song online or on the radio and want to play along instantly. So how do you determine the key of the song?

Finding the key by ear

There is no total substitute for experience with this because it can be quite abstract, but I'm going to talk you through my top tips for working out the key of a song even if you have no musical experience.

You are going to learn to hear the key of a song by ear. This works with most songs and all you have to do is listen.

You will need a device of some kind so you can check what you're hearing against an objective source. This can be a tuner with a note generator, or any instrument. I'll assume you are using your harmonica.

Pick up your harp and play different notes one at a time, over the top of the song, and pay attention to which note sounds like it has the least tension, and feels the most like "home". I can't emphasise enough that it's about the feeling of the note, so you'll get better and better at this with experience as your instincts improve.

If you have played any 2nd position harp (most blues, for example), you'll be used to the feeling of resolution that comes when you play the 2 draw note. This can be useful when trying to work out the key of a song. Get your whole collection of harps and try the 2 draw on each one - again, play it over the top of the song and see which note fits best. This is your tonal centre in cross harp so you'll probably find that you have some kind of instinctive sense of this.

Top tips for hearing the key

Don't get distracted. Make sure you're listening to the song without any distractions. If you're new to this, it will take a few listens to really zone in to the song. Make sure you're somewhere quiet so you don't get distracted by other sounds.
Listen for repeater notes. The tonic note (the one which the key is built) will likely be played or sung many times throughout the song so listen out for notes that are repeated.
Hum the tonic note. By humming along, you can centre in on the key of the song naturally. Don't overthink it - trust your instincts. Lots of us are put off from our musical instincts in early childhood, but we all have them. I believe in you!
Try to blend in. The tonic note will seem to fit into the background of the music, rather than standing out or clashing with the music.

If you have managed to determine the key, congratulations! If you want to know how to figure out which harmonica to pick up for which key, check out this lesson.

With practice, you should be able to use the above method to work out the key of most songs. However there are sometimes other methods or considerations to take into account, which we'll look at below.

Is the key of a song always the first or last chord?

Often, the first or last chord will be the key of the song. However, this is an unreliable rule to use when working out the key because it's not always true. Finishing a song with the tonic chord gives a sense of resolution, but not every song wants to resolve. It's far more important to pay attention to the overall feel of the song.

Key signatures

If you have access to the sheet music, you can check the key signature of the song; that's the little collection of sharp (#) or flat (♭) symbols in the top left corner. Count the number of sharps or flats. From this, you can determine the key:

1 sharp: G
2 sharps: D
3 sharps: A
4 sharps: E
5 sharps: B
6 sharps: F#
1 flat: F
2 flats: B♭
3 flats: E♭
4 flats: A♭
5 flats: D♭
6 flats: G♭
No sharps or flats: C

Major and minor keys

The keys written above are major keys. Each major key has a relative minor key which contains the same number or sharps/flats (you can check these on a Circle of Fifths). You can often tell if a song is major or minor from listening to it - if it feels bright and upbeat (not necessarily in lyrics but in musical feel) then it's probably major. If it feels dark or spooky, it is probably in a minor key.

Songs that change key

Lots of songs stick to one key, but some songs change key once or even multiple times. This means the tonal centre of the song becomes a new note. You can usually hear this because there will be a dramatic change when the song starts using different chords or notes. It draws your ears closer to the music, and is usually done to create a feeling of lift or progression.

If you think a song might be changing key, you can repeat the above steps for the section of the song in the new key. As a harmonica player, this might mean having multiple harps ready for one song!

Songs that don't have an obvious key

Some songs don't really have a strong and consistent tonal centre, so it doesn't make sense to think of them as being in one single key. Jazz is full of complicated chord progressions which fall outside of the basic idea of tonal centre. Jazz musicians will use a lot of the ideas discussed above, but they're often thinking about a subsection of the song rather than the entirety of the song. But don't worry, most pop, rock and blues songs won't do this. If you do progress to playing jazz, it's good to remember that thinking about subsections of songs is just the logical extension of what we've discussed above.

Check the key online

One final - and important - point: be wary of information on the internet about the key of a specific song, because sometimes the information out there can be mistaken or misleading. You're better off learning to work out the key yourself. It's much more satisfying and useful in the longterm.

I hope you have found this lesson useful. Let me know in the comments!