Benedikt Schack (also spelled as Žák, Ziak, Cziak or Schak) was born on 7 February 1758 in Mirotice, Bohemia (now the Czech Republic, then part of the Habsburg monarchy).
In 1786, Schack joined the traveling theatrical troupe of Emanuel Schikaneder, working both as a tenor and as a composer of Singspiele.
It was around this time that Schack became a friend and professional colleague of Mozart, who was gradually increasing his involvement with Schikaneder's troupe.
[7] This fairy-tale opera can be considered a kind of precursor to The Magic Flute; it employed much the same cast in similar roles.
On the very eve of his death, Mozart had the score of the Requiem brought to his bed, and himself (it was two o'clock in the afternoon) sang the alto part; Schack, the family friend, sang the soprano line, as he had always previously done, Hofer, Mozart's brother-in-law, took the tenor, Gerl, later a bass singer at the Mannheim Theater, the bass.
They were at the first bars of the Lacrimosa when Mozart began to weep bitterly, laid the score on one side, and eleven hours later, at one o'clock in the morning (of 5 December 1791, as is well known), departed this life.Mozart wrote a set of eight variations (K. 613) on Schack's aria "Ein Weib ist das herrlichste Ding" from the Singspiel Der dumme Gärtner.
Testimony for Schack's abilities as a singer comes from Leopold Mozart, who heard his debut performance with the Schikaneder troupe while it was visiting Salzburg in 1786.