Transpose Chord Progression Tool

Parse and transpose literal triad/seventh/sus chord progression with preserved suffix/slash bass and diatonic enharmonic spelling; unsupported syntax is rejected rather than guessed.

Description

A chord progression transposition should preserve quality suffixes and move explicit slash basses with the roots.

A chord progression transposition should preserve quality suffixes and move explicit slash basses with the roots. Literal syntax avoids guessing ambiguous chord labels.^[1]

Enter 1–128 symbols with uppercase roots, ASCII accidentals, optional maj7/m7/dim7/m7b5/sus2/sus4/dim/aug/m/7 and optional slash bass. Supply integer steps −28…28 and semitones −48…48. Preserve suffixes; reject target spellings beyond double accidentals.

When to use Transpose Chord Progression Tool

Use Transpose Chord Progression Tool when you need to evaluate the supplied records under the calculation and evidence rules below. Extended, nested or unsupported symbols are rejected. No harmonic reinterpretation, octave or voicing is provided.

Enter the written notes, explicit grouping, pitch observations or supported chord tokens requested. Keep scientific octaves, accidentals and caller evidence consistent.

How to use Transpose Chord Progression Tool and understand its results

Enter the written notes, explicit grouping, pitch observations or supported chord tokens requested. Keep scientific octaves, accidentals and caller evidence consistent.
Enter chordSymbols, signedDiatonicSteps, signedChromaticSemitones using the field table and calculation rules, then run the tool.
Read transposedChordSymbols. The explanation below defines the units, signs, ordering and any flags or placeholder values.
If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.

Input field	Meaning	Value type; see rules below	Requirement
chordSymbols	Chord symbols	list of string	Required
signedDiatonicSteps	Signed diatonic steps	number	Required
signedChromaticSemitones	Signed chromatic semitones	number	Required

transpose each root and slash bass with the same letter/semitone displacement

Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.

Output field	Meaning	Value type
transposedChordSymbols	Transposed chord symbols	list of string

json

{
  "input": {
    "chordSymbols": [
      "C",
      "Am",
      "F/G"
    ],
    "signedDiatonicSteps": 1,
    "signedChromaticSemitones": 2
  },
  "output": {
    "transposedChordSymbols": [
      "D",
      "Bm",
      "G/A"
    ]
  }
}

Limitations and assumptions

Extended, nested or unsupported symbols are rejected. No harmonic reinterpretation, octave or voicing is provided.

Numeric inputs, where present, must be finite. Follow the calculation-specific rules for overflow, underflow and exceptional cases. Numeric lists are limited to 10,000 entries; string lists to 128 strings of at most 128 characters each. The rules above may impose smaller limits. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors.

Alternative or Complementary methods

Use Transpose Note By Interval: Spelled transposition specifies both written-letter movement and semitone movement. A semitone shift alone cannot preserve interval spelling. For a complementary task, use Slash Chord Bass Validator: A slash symbol specifies a bass pitch independently of the chord’s root. A nonmember pedal bass can be syntactically valid.

References

Transpose Chord Progression Tool — tool.io

Similar or alternative tools

Transpose Note By Interval
Spelled transposition specifies both written-letter movement and semitone movement. A semitone shift alone cannot preserve interval spelling.
Slash Chord Bass Validator
A slash symbol specifies a bass pitch independently of the chord’s root. A nonmember pedal bass can be syntactically valid.