In the heavy metal spoof This Is Spinal Tap, tortured guitarist Nigel Tufnel plays a song in the key of D minor, declaring it to be “the saddest of all keys.” All kidding aside, while D minor isn’t inherently sadder than any other minor key, there’s still truth to the claim that minor keys are sad ones. Why? The simple answer is that the chords and scales in minor keys highlight notes that our Western ears have become accustomed to hearing as sad. Think about the intro to “Stairway to Heaven” or the melody to “House of the Rising Sun.” Both songs are in minor keys, and they both have a melancholy tinge.
The Minor Scale
Example 1 shows a C-minor scale. Play through the example and notice how this sounds different from the C-major scale in Example 2. Look closely and you’ll see there are only three different notes between these two scales: the third, sixth, and seventh notes. In the minor scale, all these of these notes are lowered one half step. The sound of these three notes gives the minor scale its sad sound.
Excerpted from Music Basics for Guitarists