Getting to know the keys
Before learning more about modulation, it’s important to understand the keys and get to know them in a practical way. There are two exercises for this that will help you become familiar with the keys. Luckily, guitar music doesn’t use too many keys - there are 24 in total - but tends to focus on just around 9-10 of them (not even half!).
Circle of 5ths
This exercise takes you through what’s called the circle of 5ths - starting at C major and going up a 5th continually. Guitar music doesn’t tend to go beyond E Major when traveling clockwise (the “sharp” keys). When traveling anti-clockwise (the ‘flat’ keys), guitar pieces rarely use those keys at all.