songleaf.diagrams

Chord diagrams for the sheet: piano keys or guitar shapes (songleaf#13).

The chords a song uses (song_chords(), in order of first use) are drawn as a strip of small diagrams. Both kinds come from the chord’s pitch classes alone (chord_tones()), so no fingering table is needed, and none has to be licensed:

• piano: a two-octave keyboard with the chord’s notes marked, in close position from the bass;

• guitar: a shape in standard tuning found by search (guitar_shape()): the lowest sounding string plays the bass (the root, or the slash bass), every chord tone sounds, the fret span is at most four frets and four fingers (notes at the lowest fret share one barre finger, unless an open string lies under the barre), and fewer muted strings, lower positions, fewer fingers and no open string between fretted ones are preferred.

The layout reserves the strip’s height before it fits the font size, so the lyrics shrink to make room (strip_height()); draw_strip() draws it.

>>> chord_tones("Cmaj7"), chord_tones("Am/G"), chord_tones("F#m7b5")
((0, 4, 7, 11), (7, 9, 0, 4), (6, 9, 0, 4))
>>> guitar_shape("C"), guitar_shape("E"), guitar_shape("G")
((None, 3, 2, 0, 1, 0), (0, 2, 2, 1, 0, 0), (3, 2, 0, 0, 0, 3))

Module Attributes

STANDARD_TUNING

Standard guitar tuning, low to high, as pitch classes (E A D G B E).

Functions

chord_tones(symbol)	The chord's pitch classes, bass first (the root, or the bass of a slash chord).
draw_strip(canvas, symbols, kind, *, left, ...)	Draw the diagrams in rows, left to right, the strip's bottom at bottom.
guitar_shape(symbol, *[, tuning, max_fret])	Frets per string, low to high (None = not played), or None if none is found.
song_chords(song)	The distinct chord symbols of song that chord_tones() reads, in order.
strip_height(n, kind, size, width, *[, style])	The height a strip of n diagrams takes across width (0 for none).

Classes

DiagramStyle([piano_width, piano_height, ...])

Sizes of a diagram, in units of the lyric font size, and its colours.

class songleaf.diagrams.DiagramStyle(piano_width=4.2, piano_height=1.5, guitar_width=1.9, guitar_height=2.2, label_scale=0.6, gap=0.7, line_color='#555555', mark_color='#222222', black_key_color='#444444')

Bases: object

Sizes of a diagram, in units of the lyric font size, and its colours.

songleaf.diagrams.STANDARD_TUNING = (4, 9, 2, 7, 11, 4)

Standard guitar tuning, low to high, as pitch classes (E A D G B E).

songleaf.diagrams.chord_tones(symbol)

The chord’s pitch classes, bass first (the root, or the bass of a slash chord).

Triads by quality (m, dim, aug/+, sus2, sus4, 5), then sevenths (7, maj7, dim7, m7b5), sixths and added ninths. None for what songleaf.harmony.parse_chord() does not read as a chord.

Return type:

tuple[int, ...] | None

songleaf.diagrams.draw_strip(canvas, symbols, kind, *, left, bottom, width, size, font, style=DiagramStyle(piano_width=4.2, piano_height=1.5, guitar_width=1.9, guitar_height=2.2, label_scale=0.6, gap=0.7, line_color='#555555', mark_color='#222222', black_key_color='#444444'))

Draw the diagrams in rows, left to right, the strip’s bottom at bottom.

Return type:

None

songleaf.diagrams.guitar_shape(symbol, *, tuning=(4, 9, 2, 7, 11, 4), max_fret=12)

Frets per string, low to high (None = not played), or None if none is found.

Return type:

tuple[int | None, ...] | None

songleaf.diagrams.song_chords(song)

The distinct chord symbols of song that chord_tones() reads, in order.

Return type:

list[str]

songleaf.diagrams.strip_height(n, kind, size, width, *, style=DiagramStyle(piano_width=4.2, piano_height=1.5, guitar_width=1.9, guitar_height=2.2, label_scale=0.6, gap=0.7, line_color='#555555', mark_color='#222222', black_key_color='#444444'))

The height a strip of n diagrams takes across width (0 for none).

Return type:

float