§ I.5 · The CLI Workshop · No. XV

Cantus-Firmus
Search.

After Mongeau & Sankoff 1990 · cf. Jeppesen 1930

Given a source melody and a corpus of pitch sequences, finds every place the source appears — exact, transposed, inverted, retrograde, or near-match. Outputs the offset, the transformation, and a similarity score derived from a Mongeau–Sankoff edit distance over pitch-interval sequences. The find-and-replace of melodic analysis.

¶ Why a command line

Musicologists studying parody masses, chorale harmonisations, and melodic citations across opera corpora need to find quotations and variants at scale. By hand the work takes weeks; in a single shell command it takes seconds. The output names where in the corpus the source occurs, what kind of transformation it underwent, and how good the match is — the rest of the analysis is yours.

¶ Invocation

$ node 06-cantus.js --source=source.txt < corpus.txt
$ node 06-cantus.js --source=chant.txt --transpositions --inversions < mass.txt
$ node 06-cantus.js --source=incipit.txt --threshold=0.85 < archive.txt
$ cat *.txt | node 06-cantus.js --source=motif.txt --retrograde > matches.txt

¶ Sample output

source: C D E F G   (intervals: 2 2 1 2)

match at  1240   exact          (similarity: 1.00)   C D E F G
match at  2103   transposition +7  (1.00)            G A B C D
match at  5441   inversion       (0.96)             G F E D C
match at  8870   retrograde      (1.00)             G F E D C
match at 12044   near (T+5,inv)  (0.81)             F E♭ D C B♭

¶ Scope

input        --source=FILE      the search melody (pitch list, MIDI or names)
             stdin / files      the corpus to search (pitch list)

flags        --transpositions   match all 12 transpositions
             --inversions       match the inverted contour
             --retrograde       match the reversed sequence
             --threshold=F      minimum similarity score (default 1.00)
             --window=N         max edit-distance window (default = source.len)

output       one line per match: offset, transformation type, similarity
             score, and the matched substring. similarity is a normalised
             Mongeau–Sankoff distance over pitch-interval sequences.

¶ References

• Mongeau, Marcelle, and David Sankoff. “Comparison of Musical Sequences.” Computers and the Humanities 24, nos. 3–4 (1990): 161–175. — the edit-distance formalism the matcher implements.
• Jeppesen, Knud. Counterpoint: The Polyphonic Vocal Style of the Sixteenth Century. New York: Dover, 1992 [1930]. — classical pedagogy on Renaissance melodic incipit-matching.

¶ Source

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