Have you heard the term tritone substitute? Do you know what it is and how to use it?
A tritone is a distance of 3 whole steps. The tritone substitute typically uses a 7th chord for the V chord whose root is 3 whole steps from the root of the V chord.
Let’s take G7 as a V chord. Db7 has a root 3 whole steps from the root of the G7 chord. Db7 is then the tritone substitute for the G7. It’s often used in a II V I progression. Dm7 G7 Cmaj7 or Dm7b5 G7 Cm7. Instead of the G7, use the Db7. Now the progression reads Dm7 Db7 Cmaj7 or Dm7b5 Db7 Cm7.
Try it out in any situation where you have a V chord, especially when the V chord resolves. The tritone substitute can also be used in secondary dominant situations.
It can be used instead of the V or in addition to the V.