Playing Guitar With Pytheory

Playing guitar (and strings) with PyTheory

PyTheory models the fretboard: chord shapes, fingerings, tablature, scale diagrams, alternate tunings, and chord identification — for guitar and ~20 other stringed instruments — plus a real-time tuner. The fretboard tools are pure Python (run a script or one-liner); the tuner is a CLI that listens to your mic.

If PyTheory isn't installed, prefer uv when available: uv pip install pytheory (or uv add pytheory in a uv project); otherwise pip install pytheory.

Fingerings, chord shapes & tab

from pytheory import Fretboard, Chord

fb = Fretboard.guitar()

print(fb.tab("Am"))          # ASCII tablature for a chord (high e on top)
# A minor
# e|--0--
# B|--1--
# G|--2--
# D|--2--
# A|--0--
# E|--x--

shape = fb.chord("Am")       # a Fingering object
shape.positions              # (None, 0, 2, 2, 1, 0)  — None = muted string
shape.string_names           # ('E', 'A', 'D', 'G', 'B', 'e')  — data model, low-to-high
print(shape.tab())           # same ASCII tab (always high-to-low display)

• Fretboard.guitar() and friends build a fretboard; .chord("Cmaj7") returns a Fingering, .tab("Cmaj7") returns the ASCII tab string directly.
• .fingering(0, 2, 2, 1, 0, 0) builds a Fingering from explicit fret numbers (low-to-high), e.g. to check a shape you have in mind.
• A Fingering has .positions, .string_names, .tones, .tab(), .identify(), and .to_chord().

Charted-chord coverage: .chord()/.tab() look the name up in a library of ~144 common voicings — every root in major, minor, 5, 6, 7, m7, maj7, 9, m9, maj9, and dim. Names outside that set (e.g. sus4, m7b5, aug, add9) raise KeyError. For those, either build the shape yourself with .fingering(...), or work from the chord's notes via Chord.from_symbol("F#m7b5") (see "Identify a chord"). CHARTS["western"].keys() lists everything charted.

Other instruments

All take the same .chord() / .tab() / .scale_diagram() API:

Fretboard.bass()        # E1 A1 D2 G2   (.bass(five_string=True) for a low B)
Fretboard.ukulele()     # G4 C4 E4 A4
Fretboard.mandolin()    # G3 D4 A4 E5
Fretboard.banjo()       # open G 5-string

Also available: mandola, octave_mandolin, mandocello, violin, viola, cello, double_bass, harp, pedal_steel, oud, sitar, shamisen, erhu, charango, pipa, balalaika, lute, twelve_string.

Alternate tunings & capo

Fretboard.guitar(tuning="drop d")     # named tunings
Fretboard.guitar(tuning="dadgad")
Fretboard.guitar().capo(2)            # capo at the 2nd fret

Named guitar tunings: standard, drop d, open g, open d, open e, open a, dadgad, half step down. For anything else, pass a tuple of open-string notes (low-to-high), e.g. Fretboard.guitar(tuning=("C2","G2","C3","G3","C4","E4")).

Identify a chord

From notes:

Chord.from_symbol("F#m7b5").identify()      # 'F# half-diminished 7th'

From a shape on the neck (great for "what chord is x02210?"):

fb = Fretboard.guitar()
fb.fingering(None, 0, 2, 2, 1, 0).identify()   # 'A minor'

Scale diagrams

from pytheory import TonedScale, Fretboard

scale = TonedScale(tonic="E2", system="western")["minor"]
print(Fretboard.guitar().scale_diagram(scale, frets=5))
#     0   1   2   3   4   5
# E| E | - | F#| G | - | A |
# A| A | - | B | C | - | D |
# ...

Pentatonic and blues scales live in the blues system, not western: TonedScale(tonic="E2", system="blues")["minor pentatonic"] (also "major pentatonic", "blues", "major blues").

Diagram images (SVG/PNG)

The ASCII diagrams above also render as clean SVG you can embed in a video, slide, or worksheet (roots in red; PNG needs the optional cairosvg):

from pytheory import Fretboard, TonedScale
fb = Fretboard.guitar()

# Chord box — open/muted markers, barres auto-detected
fb.tab_image("Am", "Am.svg")
for name in ["C", "Am", "F", "G"]:          # iterate a whole set
    fb.tab_image(name, f"{name}.svg")
fb.chord("Am").to_svg(path="Am.svg")        # same, straight from a Fingering

# Scale position shapes — e.g. the five pentatonic boxes, roots marked
pent = TonedScale(tonic="A4", system="blues")["minor pentatonic"]
for shape in fb.scale_shapes(pent):         # one box per position (1-based .index)
    shape.to_svg(path=f"pos{shape.index}.svg")

# Arpeggio map — every chord tone across the neck, labelled R/3/5/7…
fb.arpeggio_diagram("Am", "Am_arp.svg")

tab_image() covers the same ~144 charted chords as .tab(); an uncharted name raises ValueError, so build the shape and call Fingering.to_svg() instead. Pass fmt="png" (or a .png path) to rasterize via cairosvg. Each call returns the SVG string, or the path when one is given.

Nashville number charts

from pytheory import Key

prog = Key("G", "major").nashville(1, 4, 5, 1)
[c.symbol for c in prog]      # ['G', 'C', 'D', 'G']

Turn a melody into tab

Write a line as a part, print it as tablature for a guitarist:

from pytheory import Score, Duration

s = Score("4/4", bpm=120)
gtr = s.part("gtr", instrument="acoustic_guitar")
for n in ["E4", "G4", "A4", "B4", "D5", "E5"]:
    gtr.add(n, Duration.QUARTER)

print(s.to_tab("gtr"))
# e|-0--3--5--7-|-10-12|
# B|------------|------|
# ...

Score.to_tab(part_name) accepts tuning= and frets= too.

Tune up — the real-time tuner

A CLI that listens to your microphone (the user runs it themselves — suggest the ! prefix so its output lands in the session):

$ pytheory tune --instrument guitar      # strobe tuner locked to the 6 strings
$ pytheory tune --instrument guitar --chords   # strum → it names the chord
$ pytheory tune --serve                  # browser strobe page + JS pitch stream
$ pytheory tune --ref 442                # different concert pitch

Instrument presets: guitar, bass, ukulele, violin, viola, cello, mandolin, banjo. To get the target frequencies programmatically:

from pytheory.tuner import string_targets
string_targets("guitar")    # [('E2', 82.4), ('A2', 110.0), ('D3', 146.8), ...]
string_targets("guitar", reference_pitch=442)   # shifted concert pitch

Tips & gotchas

• .chord() returns a Fingering; .tab() returns the printable string. Use .tab() when you just want to show the user a chart.
• Muted strings are None in .positions and x in the tab.
• Tunings are low-to-high tuples of open-string notes; capo with .capo(n).
• Pentatonic/blues scales are in the blues system, not western.
• The tuner needs a microphone, so it's a CLI the user runs (pytheory tune), not something to call from a rendering script.
• Composing a full arrangement (chords, drums, synths, MIDI/WAV export) is the job of the composing-with-pytheory skill — this one is about the fretboard and tuning.