Substitution RULE #2: Dominant 7th Chord Substitute. This Rule simply states that the "iim7" chord may be substituted for the "V" chord. What is interesting about this rule is that the iim7 is the "ii" chord and can be inserted for (2) beats before "its" V chord creating a ii-V chord progression. Or simply substituted for the whole 4 beats creates a nice chromatic pattern for a smoother sound and feel. Check out the example.