Song Structure

Song Structure

Flow provides section declarations and Song expressions to organize music into named parts with an arrangement order.

Sections

A section is a named block of musical code containing one or more sequences:

section intro {
    Sequence melody = | C4 E4 G4 C5 |
}

Multiple Sequences

Sections can contain multiple sequences (e.g., a lead melody and a bass line):

section verse {
    Sequence lead = | E4 E4 F4 G4 |
    Sequence bass = | C3 C3 G3 G3 |
}

Empty Sections

Sections can be empty (useful for rests or structural placeholders):

section bridge {
}

Sections with Musical Context

Sections inherit the musical context they're declared in:

key Cmajor {
    section outro {
        Sequence melody = | I IV V I |
    }
}

Song Expressions

A Song arranges sections in order using bracket syntax:

section intro { Sequence mel = | C4 E4 G4 C5 | }
section verse { Sequence mel = | E4 E4 F4 G4 | }
section chorus { Sequence mel = | G4 A4 G4 E4 | }

Song mySong = [intro verse chorus]
(print (str mySong))

Repeat Counts

Use *N to repeat a section:

Song mySong = [intro verse*2 chorus verse chorus*2]

This plays: intro, verse, verse, chorus, verse, chorus, chorus.

Song Functions

getSections

Get the section names from a song:

use "@std"

Strings sections = (getSections mySong)
(print (str sections))  Note: ["intro", "verse", "chorus"]

sectionSequences

Get the sequence names within a section:

use "@std"

section mySection {
    Sequence lead = | C4 D4 E4 F4 |
    Sequence bass = | C3 G3 C3 G3 |
}

Strings seqs = (sectionSequences mySection)
(print (str seqs))

str

Convert a song or section to its string representation:

use "@std"

(print (str mySong))

Rendering Songs

Use renderSong to convert a Song to an audio Buffer:

use "@std"
use "@audio"

tempo 120 {
    timesig 4/4 {
        key Cmajor {
            section intro {
                Sequence melody = | C4 E4 G4 C5 |
            }
            section chorus {
                Sequence melody = | I IV V I |
            }

            Song song = [intro chorus]
            Buffer buf = (renderSong song "piano")
            (exportWav buf "song.wav")
        }
    }
}

Available Instruments

The second argument to renderSong selects the synthesizer:

Name	Aliases	Character
Piano	"piano"	Percussive attack with warm decay
Brass	"brass", "horn"	Bold, sustained tone
Saxophone	"sax", "saxophone"	Reed-like character
Flute	"flute"	Pure, breathy tone
Organ	"organ"	Sustained, multi-partial timbre
Strings	"strings"	Smooth bowed-instrument-like timbre
Bell	"bell"	Inharmonic bell / chime character
Drums	"drums", "drum"	Percussive, pitched drums
Sine	"sine"	Clean sine wave

Custom wavetables registered via oscillator(name, ...) also work here. You can also pass a Flow Function as a custom instrument — see Audio and Synthesis.

Complete Example

use "@std"
use "@audio"

tempo 120 {
    timesig 4/4 {
        key Cmajor {
            section intro {
                Sequence melody = | C4 E4 G4 C5 |
            }

            section verse {
                Sequence lead = | E4 E4 F4 G4 |
                Sequence bass = | C3 C3 G3 G3 |
            }

            section chorus {
                Sequence lead = | G4 A4 G4 E4 |
            }

            section bridge {
                Sequence mel = | A4 G4 F4 E4 |
            }

            section outro {
                Sequence melody = | I IV V I |
            }

            Song fullSong = [intro verse*2 chorus bridge outro]
            Buffer rendered = (renderSong fullSong "piano")
            Buffer final = rendered -> fadeIn 0.3 -> fadeOut 0.5
            (exportWav final "full_song.wav")
            (print "Song exported!")
        }
    }
}

When to Use Sections

• Organizing composition: Break music into logical parts (intro, verse, chorus, bridge, outro)
• Reuse: Reference the same section multiple times with *N repeats
• Clarity: Named sections make the arrangement readable at a glance

Exporting to MIDI

A Song can also be exported to a Standard MIDI File, preserving tempo, time signature, and key:

(writeMidi "my_song.mid" fullSong)

See Playback and Export.

See Also

• Note Streams - Writing sequences within sections
• Musical Context - Context blocks around sections
• Audio and Synthesis - Rendering and synthesizers
• Voices and Tracks - Lower-level multi-track rendering
• Chord Progressions - Voice-led chord sequences
• Playback and Export - Playing and exporting songs