Its basically a way of plotting how to ride a beat in a particular way...something that's very hard to teach. And believe me, a lot of professionals use this:
The flow diagram is a system of notation to show how flow works. Every beat has 4 counts (1...2...3...4). If u want to write to a specific beat, or ride the beat in a particular way, the use of a flow diagram can help you plot this visually. Create a table with 4 columns representing the four parts of the beat. Each row will be filled by a line from your verse. Assign the words in each line to the columns to plot which part of the beat they come in at.
To give an example, here are the opening lines from the Pharcyde’s track “Drop,” from the album Labcabincalifornia, written normally:
Let me freak the funk, obsolete is the punk that talks
More junk than Sanford sells. I jet propel at a
Rate that complicate their mental state as I invade their
Masquerade. They couldn’t fade with a clipper . . .
Now here are the same lyrics, this time shown in the flow diagram:
Beats and Bars
The numbers along the top of the diagram represent the beats in the music, and each new line represents a new bar of music. A bar is simply a way of measuring a unit of time in music—in almost all hip-hop tracks, one bar is four beats.
To see clearly how the lyrics match up to the beats and bars, simply listen to the song in the example. In the first line, you can say “let . . . funk . . . lete . . . punk . . .” along to the lyrics and it is the same as counting “one . . . two . . . three . . . four . . .” in the music. That means those are the places where each beat falls:
Each line of the diagram is four beats, or one bar of music. The example below shows the first two bars:
The first bar has the lyrics “Let me freak the funk, obsolete is the punk that talks,” and the second bar has the lyrics “more junk than Sanford sells. I jet propel at a . . .”
Many rappers write down their flows by counting bars (Rock of Heltah Skeltah says, “When I’m writing it on paper, I do count my bars—I mark them down”), and using one line to represent one
bar is a common way of doing so. As Crooked I says, “I used to get the legal pad, man, the yellow one, and I used to write each bar as one line, so at the end, 16 lines, 16 bars.”