MusicReasonChords and Harmony
What can I borrow from a parallel mode?
Choose a tonic, the current major or minor mode, and a parallel source mode sharing that same tonic. This tool builds the source mode's own diatonic triads and flags exactly which scale degrees differ from the current mode's, since provenance from a genuinely parallel collection is what makes a chord "borrowed" here, not every chromatic chord in general.
Answer
Want to learn more? Chord Function, Cadence, and Substitution
Understand
Modal interchange, also called modal mixture, means borrowing a chord from a parallel collection that shares the current key's tonic, not its key signature. C major and C Aeolian share the tonic C but differ in several scale degrees, so a chord built on C Aeolian's own third or sixth degree brings genuinely different pitches into an otherwise C-major context, while the tonic itself never moves.
Worked examples
C major borrowing from its parallel Aeolian includes an A-flat major triad(from Aeolian's sixth degree) and an E-flat major triad (from Aeolian's third degree), both genuinely different from C major's own vi (A minor) and iii (E minor) chords at those same scale degrees. The source tonic, C, never changes across any of these borrowed options.
Method and limitations
The tool constructs the source mode's own scale from the declared tonic, stacks a triad at every scale degree using the source mode's own interval pattern, and separately constructs the current mode's triad at that same degree number for comparison. Only degrees whose root pitch class differs between the two collections are flagged as changed; every degree is still shown, changed or not, since an unchanged degree is meaningful context too. This tool does not label every chromatic chord in a piece as borrowed, only chords whose provenance from a stated parallel collection is being explicitly compared here, and it does not resolve the boundary between mixture and an outright modulation.
Borrowing from Dorian instead of Aeolian changes which degrees actually differ: Dorian shares its sixth degree with the current major mode (both a plain major sixth above the tonic), so a Dorian source flags fewer changed chords than an Aeolian source does for the same major-key tonic. This is exactly why the source mode is a deliberate, named input here rather than an assumed default; different parallel collections genuinely offer different borrowed options, not merely different labels for the same result.