Turning Numbers Into Music

The process of turning a number chart into actual music comes down to knowing the general style and conventions of a genre of music.

Overall Style

Each genre of music has an overall style that all musical material is filtered through. This means that the way chords are played (voicing, rhythm, texture, etc.) will change depending on the genre and style of a song. The way chords are played even change within different sections of the same song (quiet/loud parts, heavy/soft parts). Another element that defines musical style is the use of extra harmonies that characterize a particular sound of a genre (modern, jazzy, twangy, rocky, etc.). Rather than notate every one of these details in a chart, musicians routinely use simple charts as a harmonic roadmap and infer the stylistic details while playing in a certain genre. Most popular music fits within a replicable style that can eventually be picked up in seconds. Learning these specific styles and applying them to simple chord progressions is an essential part of music making.

For example, a professional musician, if called on to play many genres of music back-to-back, would probably chart the songs out in numbers and label each tune with the genre it most closely resembles. Every chart's numbers might look indistinguishable (a bunch of 1, 4, and 5 in different orders, like 90% of any song ever written). However, when filtered through a specific style, the numbers are translated into the way chords are routinely played in that style. In this way, musicians come to unknown music knowing the style and conventions and knowing what sounds great to add and what must be omitted. 

Above all, listening and learning the overall style of a song is the tried and true way to implement that style on countless other similar songs.

The songs of the Beatles are a good example of the incredible variety in musical style. The characteristic elements that define each genre turn the relatively simple charts for the below tunes into actual music:

• Blues- (Roll Over Beethoven, Boys, Little Child, She's A Woman). Iconic walking bass lines, moveable riffs, dominant 7 chords, and added chromatic notes are some of the elements that give blues music its signature sound. These elements can be automatically added on when playing the simple chord progressions found in these songs. Many blues tunes are based directly or roughly on the 12 Bar Blues form.

• Country/Western- (I've Just Seen A Face, I'm A Loser, Honey Don't, I'll Cry Instead). A similar style to the Blues, Country music uses similar techniques (standard chord forms, walking bass, twangy licks, 7th chords, driven by acoustic strumming) to define its sound. Many American-based genres like Blues, Folk, Country, and Jazz music share historical roots and therefore stylistic trends.
  

• Rock- (Helter Skelter, Revolution). Rock music puts emphasis on Power Chords (chords with just the Root/5th and no 3rd), and rhythmic riffs played by the whole band. After the Beatles, Rock and Roll really built itself around the direct sound of the power chord.
  

• Oldies- (P.S. I Love You, Do You Want To Know a Secret, Ask Me Why). Oldies music from the 1950's and 60's tended to use standardized chords with little or no added notes, homogeneous strum patterns, and little dynamic contrast.
  

• Jazz- (Something, Michelle, Across The Universe). While definitely not jazz per se, these songs treat chords more like they are treated in jazz, as different shades of color. Songs like these tend to include many chords (in and outside of the key), complex arrangements, key changes, and chords with specific added notes (different colors/flavors). These songs are more suited for advanced players and often don't fare well being watered down at all.
  

• Pop- (Let It Be, Hey Jude, In My Life, Eleanor Rigby). Pop focuses on a strong, singable melody, simple chords, relatable lyrics, the use of keyboards or synths to fill up the space over guitars, and catchy hooks.

Often the Beatles and countless other groups were inspired by and combined the above styles and influences to seamlessly create unique music. As always, the ear should have the last word as to what sounds good within a certain style of song.

Adding Detail to Songs

Melodic Parts

A more advanced style is one that incorporates melodic parts into the chords (Here Comes The Sun, Blackbird, Lady Madonna, Norwegian Wood). This can sometimes be right under or within the current chord on one's instrument, or more difficult and unintuitive. For example, The chords to the beginning of Here Comes The Sun are 1, 1, 4, 5. Simply strummed, no-one would recognize that progression as Here Comes The Sun. However, the added melodic notes in those chords as played on the record immediately identify the song (this goes for the other examples listed). The more ear training one does (a by-product of reading number charts), the easier it becomes to hear licks, melodies, and exact parts. Musicians can and should incorporate such melodic ideas when musically appropriate. 

Bass Lines

Songs are sometimes based heavily on bass line riffs or walking bass parts (Day Tripper, Penny Lane, Come Together, and Money). Learning iconic bass lines is a great idea on any instrument because they really carry the tune. Most foundational bass lines are notated in Chordal charts.

Modern Sounding Pop Chords-

Modern popular music often includes tones from the 1 chord added to all the chords in the key, creating a more smooth, harmonically detailed sound (and more complex 4, 5, and 6m chords). 

This convention changes a chord progression like:
1,  4,  6m, 5 (In G: G, C, Em, D) to
1, 4add9, 6m7, 5sus4 (G, Cadd9, Em7, Dsus4)

Notating every song in this style with the added detail in the 2nd line would be redundant. These chords are used so frequently and are strongly associated with the style of modern popular music that it's easy to know when to swap out the simple to read 1, 4, 6m, 5 with the more style-appropriate and modern 1, 4add9, 6m7, 5sus4. Therefore, songs with these chords are notated as simply as possible to aid in ease of reading. These chords can be used any time they sound good or fit in the style of a song. You’ll start to develop an intuition that informs how best to recreate the 'sound' of a certain genre of music and when to employ modern-sounding chords or not.

Examples of Modern Sounding Chords In Action:

Ed Sheeran's The A Team (A):

Actual Chorus Progression: 2m7, 4add9, 1, 5/7add4
Chorus Notated in Chart: 2m, 4, 1, 5/7

Radiohead's High And Dry (E):

Actual Whole Song Progression: 2m7, 4sus2, 1, 1
Notated in Chart: 2m, 4, 1, 1

Bruno Mars' Just The Way You Are (F):

Actual Whole Song Progression: 1, 1, 6m7, 6m7 / 4sus2, 4sus2, 1, 1
Notated in Chart: 1, 1, 6m 6m / 4, 4, 1, 1

Many songs are straightforward where the chords are played in a standard and predictable way with no added notes. These kinds of songs are perfect for beginners due to the short distance between learning the chords in the song and making those chords sound like the song.