Sus Chord vs Triad Classifier

Distinguish exact third-replacing sus2/sus4 sets from tertian triads and mixed/added-tone ambiguity; presence of a second/fourth alone does not imply suspension.

Description

Suspended chord sets replace the third with a second or fourth.

Suspended chord sets replace the third with a second or fourth. Complete pitch-class collections differ from a missing-third claim alone.^[1]

Enter 1–128 integer root-relative offsets 0–127. Reduce modulo12, remove doublings and compare exact sets; return quality and whether class3 or 4 is present.

When to use Sus Chord vs Triad Classifier

Use Sus Chord vs Triad Classifier when you need to evaluate the supplied records under the calculation and evidence rules below. Extra/missing tones can be unrecognized. No root detection, inversion or resolution is inferred.

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

How to use Sus Chord vs Triad 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 rootRelativeChordSemitones using the field table and calculation rules, then run the tool.
Read suspensionOrTriadQuality, thirdPresent. 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
rootRelativeChordSemitones	Root relative chord semitones	list of number	Required

Enter 1–128 integer root-relative offsets 0–127. Reduce modulo12, remove doublings and compare exact sets; return quality and whether class3 or 4 is present.

{0,2,7}→sus2; {0,5,7}→sus4; otherwise compare tertian triads

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

Output field	Meaning	Value type
suspensionOrTriadQuality	Suspension or triad quality	string
thirdPresent	Third present	boolean

json

{
  "input": {
    "rootRelativeChordSemitones": [
      0,
      2,
      7
    ]
  },
  "output": {
    "suspensionOrTriadQuality": "sus2",
    "thirdPresent": false
  }
}

Limitations and assumptions

Extra/missing tones can be unrecognized. No root detection, inversion or resolution is inferred.

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. A successfully returned false flag is an evaluated outcome; its meaning is explained above.

Alternative or Complementary methods

Use Chord Quality From Intervals Classifier: Tertian triad quality is defined by a complete root-relative pitch-class set. Octave doublings do not change the set. For a complementary task, use Seventh Chord Type Classifier: Seventh quality depends on the complete root-relative pitch-class set. Doublings do not create additional chord members.

References

Sus Chord vs Triad Classifier — tool.io

Similar or alternative tools

Chord Quality From Intervals Classifier
Tertian triad quality is defined by a complete root-relative pitch-class set. Octave doublings do not change the set.
Seventh Chord Type Classifier
Seventh quality depends on the complete root-relative pitch-class set. Doublings do not create additional chord members.