Pitch classes identify a formula
C, E and G form the major-triad interval pattern when measured from C. Duplicating C in another octave does not add a new pitch class. The dictionary compares exact sets, so adding a seventh changes the available names.
The bass affects the label
Enter octave numbers so the tool can find the lowest actual note. E3 G3 C4 is a C-major chord over E, while C3 E3 G3 is root position. Without context, neither spelling establishes the harmonic function in a song.
Some collections match more than one formula, such as a sixth chord and a related minor seventh. Try the exported chord MIDI, examine the surrounding progression, and choose a name that communicates the part clearly.
Enter a small chord precisely
Choose Identify a chord from notes and enter C4 E4 G4 Bb4. The distinct pitch classes match a dominant-seventh formula rooted on C. Now enter E3 G3 Bb3 C4: the pitch collection is unchanged, but E is the lowest actual note, so the interpretation shows an inversion over E. Use octave numbers whenever the bass matters.
Duplicate notes do not create extra chord members. C3 C4 E4 G4 still contains only C, E and G as pitch classes. Conversely, adding D changes the set and can produce an add9 interpretation. A no-match result means the exact collection is outside the implemented dictionary; it does not mean the notes are musically invalid.
Listen without overinterpreting the name
The exported chord MIDI sounds the entered notes together for two seconds. Use it to check spelling and register, then place the chord back into its progression. The dictionary does not infer omitted roots, recognize audio, assign Roman numerals or analyze voice-leading. Suspensions, extensions and polychords may need a different description even when a simpler exact formula happens to match.