Chord Inversion Calculator - Bass Note and Slash Notation

A chord inversion calculator is a music-theory tool that takes a root note, a chord type, and an inversion level and returns the bass note, the slash-chord notation, the chord tones from bass to top, and the inversion label. It rotates the chord's note list so any chord tone can sit in the bass, which is how a C major chord becomes C/E in first inversion and C/G in second inversion.

• • Read slash-chord symbols: Pick the upper chord symbol and the bass note from a chart, then read off the slash notation, the inversion label, and the interval stack.
• • Plan a stepwise bass line: Switch between root position, 1st inversion, and 2nd inversion to keep the bass moving by step or common tone.
• • Practice piano and guitar voicings: Use the chord-tone list (bass to top) as the voicing on piano, and rearrange the chord tones to locate open guitar shapes that put the third or fifth in the bass.

The chord inversion calculator returns one result row for every (root, chord type, inversion) combination, so a single chord can be viewed in root position, 1st inversion, 2nd inversion, and (for seventh chords) 3rd inversion without leaving the page.

When the chord symbols and inversions need to be built from the same root and chord type, the Chord Calculator builds the original triad or seventh chord that this calculator then inverts.

The chord inversion calculator combines the root note, the chord type, and the inversion level through a single rotation step. It walks the chromatic scale from the root by the chord type's semitone intervals, then rotates the resulting note list by the inversion number using modular arithmetic so the requested chord tone lands in the bass.

• rootNote: Pitch class for the root, from the 17-value dropdown.
• chordType: Chord quality. Triads support 3 inversions and seventh chords support 4.
• inversion: Number of positions the chord-tone list is rotated before stacking.
• baseNotes: Original chord notes in root-position order, built by walking the chosen enharmonic chromatic scale from the root.
• bassNote: First element of invertedNotes, which is baseNotes[inversion mod chordLength].

The interval stack shows the semitones between consecutive chord tones from the bass upward, so a 1st inversion major triad reads 3, 5 instead of the 4, 3 stack of root position. That single number sequence is what tells a pianist or guitarist whether the same chord tone order is being repeated higher up the keyboard or fretboard.

According to Wikipedia - Inversion (music), a chord inversion is a chord in which a chord tone other than the root is in the bass, and slash notation writes the bass note after a slash, as in C/E for a C major triad with E in the bass.

When the inverted chord and the rest of a progression need to move to a new key, the Chord Transposer keeps the same slash-bass notes and chord qualities while shifting every root by the same number of semitones.

Four ideas from music theory explain why a single chord can be stacked several different ways without changing its quality, and they appear in the result row for every inversion the user builds.

Modular arithmetic is what makes the rotation step work: rotating the chord-tone list by the inversion number and wrapping with mod n moves the requested chord tone into the bass without leaving the original pitch class set.

The rotation step that moves a chord tone into the bass uses the same mod n wrap-around the Modulo Calculator handles for any positive modulus, so the inversion number can be any non-negative integer and the bass always lands on a real chord tone.

Five short steps take you from a root note, a chord type, and an inversion level to a complete slash-chord symbol with the bass note, the chord tones from bass to top, and the inversion label.

1. 1 Pick the root note: Choose the pitch class for the root from the 17-value dropdown. Pick the sharp or flat spelling that matches the key you are working in.
2. 2 Pick the chord type: Choose one of the 11 chord qualities. Triads give 3 inversions; seventh chords give 4.
3. 3 Set the inversion level: Enter 0 for root position, 1 for first inversion, 2 for second inversion, or 3 for third inversion on a seventh chord. The result panel clamps 3 to 2 for triads.
4. 4 Read the inversion and slash chord: The result row prints the inversion label and the slash-chord symbol together. C/E reads as 'C major in first inversion with E in the bass'.
5. 5 Read the bass note and chord tones: The bass note row shows the chord tone in the bass. The chord tones row lists the same chord tones from bass to top, which is the voicing order on a keyboard or fretboard.

Practical example: a worship leader asks the band to play a C chord with the G in the bass. Set root note to C, chord type to Major triad, and inversion to 2. The result row reads 2nd inversion, bass note G, chord tones G, C, E, slash chord C/G, so 2nd inversion is the right pick for that voicing.

When an inverted chord is heard without knowing the upper symbol, the Chord Finder names the chord from the bass-to-top note list and lists the closest alternative spellings side by side.

Five practical reasons to use the inversion tool instead of paging through a music-theory text or working the rotation out by hand.

• • Slash-chord notation in one row: Read the standard C/E, C/G, G7/F shorthand straight from the result row.
• • Self-consistent inversion labels: The inversion label, the bass note, and the slash-chord symbol all come from the same rotation step.
• • Visual interval stack: The interval stack column shows the semitones between consecutive chord tones from the bass upward.
• • Covers triads and seventh chords: Eleven chord qualities spanning major, minor, augmented, diminished, suspended, dominant 7, major 7, minor 7, half-diminished 7, and diminished 7 all invert from the same result row.
• • Enharmonic spelling follows the root: The bass note keeps the same sharp or flat spelling as the chosen root, so an F# root renders every inversion with sharps and a Gb root renders every inversion with flats.

Inversions are the standard tool for smoothing out bass lines. The calculator returns the bass note next to the slash chord so a piano, guitar, or bass player can read the next chord change without guessing which chord tone sits on the bottom.

Four practical variables change the result row and two approximation caveats explain why the tool is a music-theory reference rather than a substitute for ear training.

• • The tool is a music-theory reference, not an ear-training tool. It does not judge whether a particular inversion sounds better in a progression, and it does not teach voice leading between two adjacent chords.
• • The result row uses 12-tone equal temperament. Microtonal intervals, just intonation, and non-Western tunings are not represented in the interval stack column.

Slash-chord notation only names the bass note and the upper chord symbol, so two voicings of the same inversion (open vs closed) read the same on paper. The interval stack column gives the closed voicing order, which is the order a pianist reads on the staff.

According to Wikipedia - Slash chord, a slash chord (also called a compound chord) is written as X/Y where X is the upper chord and Y is the bass note, and the bass note is the lowest sounding pitch in the chord.