Chord Quality From Intervals Classifier

Classify exact root-relative tertian triad pitch-class sets with octave duplicates collapsed; returns unrecognized for extras/missing tones, not root inference or seventh classification.

Description

Tertian triad quality is defined by a complete root-relative pitch-class set.

Tertian triad quality is defined by a complete root-relative pitch-class set. Octave doublings do not change the set.^[1]

Enter 1–128 integer offsets0–127. Reduce modulo12, deduplicate and compare exact patterns; return quality or unrecognized plus distinct class count.

When to use Chord Quality From Intervals Classifier

Use Chord Quality From Intervals Classifier when you need to evaluate the supplied records under the calculation and evidence rules below. Extra or missing pitches remain unrecognized. No root detection, seventh quality or audio analysis is supplied.

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

How to use Chord Quality From Intervals Classifier 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 rootRelativeSemitoneOffsets using the field table and calculation rules, then run the tool.
Read tertianTriadQuality, distinctPitchClassCount. 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
rootRelativeSemitoneOffsets	Root relative semitone offsets	list of number	Required

Enter 1–128 integer offsets0–127. Reduce modulo12, deduplicate and compare exact patterns; return quality or unrecognized plus distinct class count.

major={0,4,7}; minor={0,3,7}; diminished={0,3,6}; augmented={0,4,8}

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

Output field	Meaning	Value type
tertianTriadQuality	Tertian triad quality	string
distinctPitchClassCount	Distinct pitch class count	number

json

{
  "input": {
    "rootRelativeSemitoneOffsets": [
      0,
      4,
      7,
      12
    ]
  },
  "output": {
    "tertianTriadQuality": "major",
    "distinctPitchClassCount": 3
  }
}

Limitations and assumptions

Extra or missing pitches remain unrecognized. No root detection, seventh quality or audio analysis is supplied.

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 Seventh Chord Type Classifier: Seventh quality depends on the complete root-relative pitch-class set. Doublings do not create additional chord members. For a complementary task, use Sus Chord vs Triad Classifier: Suspended chord sets replace the third with a second or fourth. Complete pitch-class collections differ from a missing-third claim alone.

References

Chord Quality From Intervals Classifier — tool.io

Similar or alternative tools

Seventh Chord Type Classifier
Seventh quality depends on the complete root-relative pitch-class set. Doublings do not create additional chord members.
Sus Chord vs Triad Classifier
Suspended chord sets replace the third with a second or fourth. Complete pitch-class collections differ from a missing-third claim alone.