One of the first steps to understanding music theory on guitar, is learning about keys. So what exactly is a key on guitar?
A key denotes the root of a scale that a group of given chords or notes fall into. For example, if a song begins on a G chord, and then transitions to C and D chords, before returning again to G, this song would be in the key of G. For soloing purposes, this means a G major scale could be used to play or sing over the song.
Once you understand this, some other logical questions emerge, like how do you figure out what key a song is in? We’ll answer that question and some other common questions about guitar keys in the sections below.
How Do You Know What Key A Song Is In?
One of the quickest and easiest ways to figure out a key of a song, is to determine the chord that the song begins and ends on. Remember in our example above, where the song began and ended on a G major chord? One could quickly conclude that the song was in G major, or at least that the G major scale could be an appropriate choice for playing a guitar solo.
However, this method isn’t completely foolproof, as some songs don’t begin on the chord of the key that they’re in. If you use this method and the key still doesn’t sound correct, you can look up a tab or chord chart on sites like Ultimate Guitar for help.
Why Do Guitar Keys Matter?
You may also be wondering why it even matters what key a song is in. To be fair, you don’t absolutely have to know what key a song is in in order to play it. If all you want to do is play the chords of the song, then all you really need to know is those chords – and what key it’s in is not a huge concern.
Guitar keys become a lot more important, however, if you want to play a solo or improvise over a song, or if you’re trying to learn a song by ear. If you’re doing any of those things, they become a lot easier once you have the foundation of knowing what key you’re in. If you don’t know the key, you’re at the mercy of trying to improvise over each chord individually, rather than having an overarching scale that will work over the whole song.
Guitar Keys Explained
Each key has it’s own 7 notes, and also contains a variety of chords that can be used. When someone uses the phrase “playing in key” or asks what key a given song is in, they’re referring to the “tonal center” around which these chords or notes of a song are based in.
To learn how notes and chords go together to form a key, I recommend Marty Schwartz’s excellent YouTube videos. They’re very practical and don’t bog you down with unnecessary music theory. Here’s a great one to get started: