The Nashville Number System is a simple way to write and read chord progressions using numbers instead of chord names. Each number represents a chord built on a scale degree of the key (for example, in the key of C, 1 = C, 4 = F, 5 = G). This allows musicians to easily change keys while keeping the same progression. In worship music, the system is especially helpful for flexibility, quick communication, and playing together smoothly when keys need to be adjusted