MusicReasonChords and Harmony
What chord fits this bass note?
Declare which note is sounding in the bass, then add the notes above it. This tool identifies candidate chords with that bass in place, and states plainly whether the bass is the chord's own root, a member tone in inversion, or an added bass beneath a chord that does not otherwise contain it.
Answer
Understand
A bare note set like C, E, and G is ambiguous about which note is meant to sound lowest; stating the bass explicitly resolves that and changes how the result reads. When E sounds below C and G, the chord is still C major, but now specifically C major in first inversion, written C/E. The bass is a genuine member of the chord's own template, just not its root. When the declared bass is not a member of any matching template at all, this tool cannot silently promote it into the chord; that case instead surfaces as an added bass, a distinct harmonic idea from an inversion.
Worked examples
C, E, and G with E declared as the bass identifies as C/E, first inversion, with a single unambiguous best match. C, D, and G with C declared as the bass is genuinely ambiguous: the same three notes support both C sus2 (root position, since the bass equals the chord's own root) and G sus4 (with C as an added bass beneath a G-rooted sus chord) as equally strong exact matches. The tool reports both rather than guessing.
Method and limitations
Every declared note, including the bass, is treated as a candidate chord root against the same locked template vocabulary the Chord Identifier uses, since the underlying pattern matching is identical; this tool only adds the bass-first framing and the inversion-versus-added-bass distinction on top. A match is ranked an inversion only when the declared bass is itself one of the winning template's tones and is not that template's own root; otherwise a valid match with a different root is reported as an added bass. Co- equal exact matches are reported as alternatives rather than a forced single answer, and a note set that explains no chord returns a clear no-result state instead of a guess.
A bass note declared equal to a winning template's own root is never mislabeled an inversion or an added bass; it is simply that chord in root position, the ordinary case. The inversion and added-bass labels only apply once the declared bass differs from a candidate's root, and even then the two labels are never interchangeable: an inversion always uses one of the chord's own already-counted tones as the bass, while an added bass introduces a pitch class the plain chord template did not already require.