, K. 561, is a canon in A major for four voices a cappella by Wolfgang Amadeus Mozart; Mozart entered this work into his personal catalogue on 1788 as part of a set of ten canons.
The canon is written in the time signature of cut common time and in the key signature of A major. The theme is 16 bars long; each of the four voices enters after four bars.
The original lyrics are probably by Mozart himself; they include the words for "good night" in five different languages (Latin, Italian, French, English, and German). The phrase "", found in the fourth-to-last and third-to-last lines, closely resembles a similar expression found in a postscript to one of Wolfgang's letters by his mother, written to his father; also in Mozart's letter from to his sister.
The completely expurgated version found widespread distribution in traditional German '.