The ii–V7-I can be further modified by applying a tritone substitution to the V7 chord, replacing it with the II7 chord. This is possible because the II7 has the same third and seventh as the V7, but inverted; for example, the third and seventh of G7 are B and F, while the third and seventh of D7 are F and C, which is enharmonic to B. Performing this substitution (in this case, changing Dm7–G7–Cmaj7 to Dm7–D7–Cmaj7) creates smooth chromatic movement in the chord roots—the root of the ii (D) moves down a half-step to become the root of the II7 (D), which moves down another half-step to become the root of the I (C).