The Rest of the Theory
The Nashville Number system doesn't explain all the music theory you need to know and there are some little things like rhythm and harmony that you might want to take a look at if you want to make millions of dollars.Harmony
From Ancient hymns, Renaissance choirs, and barbershop quartets to the Statler Brothers, the Temptations, and N'Sync, vocal harmony is one song element that almost never goes out of style.
Studying the harmony styles of current bands can help you write songs with those groups in mind. Certain kinds of melodies and chord structures lend themselves to certain kinds of harmony arrangements and vice versa. Knowing these things will help you to write a song with the kind of harmonies you want or find the right harmonies for a song you've already written.
In a broader sense, harmonic theory will help you understand how instruments and voices work together, and how bass lines, chord structures, and other instrumental parts work within a song to build harmonic structure that surrounds your melody and reinforces it. This gives you more power to influence things like prosody, dynamics, and “feel” in your songwriting.
Knowledge of harmony can be a troubleshooting tool. When the chords of a song and the vocal harmonies sound right separately but clash when put together, check to see if they have conflicting harmonies. If so, they may form chords that sound unpleasant to the ears. Change one or the other to fix this problem.
Knowledge of rhythm helps you make sure that everything synchs up. It can aid in finding better flow and symmetry in your lyric meter and communicating with bandleaders, studio musicians, and co-writers.
Familiarity with different kinds of beats expands your groove options for songwriting. Knowing the difference between a straight beat and a shuffle or between a Bossa Nova and a Samba saves you from having to communicate by making mouth sounds or pounding on the nearest flat surface.Analyzing the Greats
Most songwriters can proudly list several other songwriters who influenced them and readily admit to studying hit songs and what makes them work. Without some grounding in theory, this means a lot of guessing and trying to blindly capture the feel of something.
Music theory can help you to understand exactly how a song is put together and why it works. This gives you more options and information to work with and leaves you more time for writing your own songs.
These days, rhythmic differences are the main factors defining various genres. Learning the rhythms of a particular style of music can be the first — and most important — step to being able to write songs in that genre. Knowing a little about rhythm can put you on the path to becoming a very versatile songwriter.