7th chords are a great place to start when expanding your knowledge of chords beyond basic major and minor chords. In this guitar lesson, we'll cover the four main types of 7th chords: major 7 chords, dominant 7 chords, minor 7 chords, and minor 7 flat 5 chords.
To make a major 7 chord, start out with a basic major triad. You'll have a root, a major 3rd, and a 5th. To turn that into a major 7 chord you just need to add the 7th scale degree. In this case, we're using a C major triad with the notes C, E, G. To turn it into a C major 7 chord we just need to add the B note.
Dominant 7 chords are very similar to major 7 chords and only differ by one note. To turn a major 7 chord into a dominant 7 chord, you just need to lower the added note by a half step. So you'll have a root, 3rd, 5th, and a flat 7. Which means if we're still using our C major triad, we'd be adding a B flat. This chord is commonly used in blues music.
To make a minor 7 chord, you'll continue where you left off with a dominant 7 chord. From there, you just need to lower the 3rd. So your major 3rd becomes a minor 3rd. This shape can be a little impractical, and it's only being shown for the sake of understanding how the chord is made. It's recommended to use a more simple shape in practice.
The last 7 chord we'll look at is the minor 7 flat 5 chord (or m7b5). This chord isn't used too often, but it's the naturally occurring 7th chord in a key, so it's worth knowing. For this chord, all we need to do is take a minor 7 chord and lower the 5th.
Try each of these chords out and work on understanding the theory behind them. They're a great way to add some flavor to your playing!