K.2 89a (K.6 73i), attributed to Wolfgang Amadeus Mozart, is a simple canon exercise in A major for four sopranos in unison. This piece closely resembles the Kyrie K.89, which is also written for four sopranos in unison. However, unlike the Kyrie, which serves a clear liturgical purpose, K.2 89a (K.6 73i) seems more like an incomplete experiment.

In this supposed composition, Mozart wrote only six measures for four voices. The piece is stagnant, with no modulations as it remains firmly in A major throughout. There is an overwhelming amount of repetition, suggesting a lack of imagination, even if one were to excuse it as a contrappuntal exercise.

This is where things become problematic. Although Wolfgang arranged the piece for four voices, the canon actually requires five to achieve complete harmonies. Without a fifth voice, the piece sounds incomplete, leaving discordant gaps that Mozart, if he had composed it, would surely have recognized.

The fifth voice is not indicated in the original manuscript, yet modern editors, including the Neue Mozart-Ausgabe (NMA), have added it in parentheses. This fifth voice logically enters at measure 13, filling the incomplete harmonies that otherwise sound weak. Curiously, Mozart left the final three measures filled with pauses, which suggests he may not have fully solved the harmonic puzzle presented by the canon.

Moreover, Amadé didn’t bother writing out any text, leaving many notes in a disjointed state, as though he were copying from an original source that had syllables of text he ignored. In an attempt to fill this void, modern editions have introduced whimsical verses, such as:

“Hei, wenn die Gläser klingen, so lasst uns alle fröhlich sein, und lasst uns lustig singen, ja singen ja lustig singen, am Tisch beim kühlen Wein.”
(“Hey, when the glasses clink, let’s all be merry and sing happily, sing sing joyfully, at the table with cool wine.”)

Breitkopf’s edition, unlike the NMA, corrected the canon by discreetly adding the fifth voice without explicitly saying so, transforming the piece into a Kanon für 5 Stimmen (canon for five voices) to make it more marketable.

Given that this is clearly a poorly resolved copy of a canon by an anonymous author, with Mozart forgetting the fifth soprano’s entrance, it should neither be considered an original composition nor included in his official catalogue.