The Nashville Number System is a shorthand method of transcribing music by using numbered scale degrees instead of chord names; it does not follow exact textbook theory practices, but is ingeniously practical for its simplicity. Its utility is that, for any given key, the tonic note is always number 1. So a song in the key of C with the chord progression C - F - G - C becomes 1 - 4 - 5 - 1. If the key is transposed up a half step to C# – F# – G# – C#, it is still 1 – 4 – 5 – 1 in the Nashville system. It works only if the key center of the chart is known and agreed upon by all reading it. For practical purposes, it assumes that all keys are major; it further assumes all It assumes that player instinctively knows the relative intervals based on the key designation.