The next mode is obtained when F is taken as the tonic. This is called the Lydian mode (see Figure 20.5).
The Lydian mode is virtually the same as the F major mode, except that the fourth degree is sharp. This produces an augmented fourth with the tonic, which, when used properly in a modal tune, can produce a euphoric sense. To appreciate this, try experimenting with it—it can produce some really interesting tunes. The theme from The Simpsons is probably the most famous recent example of a Lydian-inspired tune.
Sometimes the Lydian mode is used with the flat seventh, where it is called the