Johann Sebastian Bach's 'Actus Tragicus' (BWV 106, commonly known as 'Gottes Zeit ist die allerbeste Zeit') is a profound sacred cantata, but the title is also sometimes applied to piano transcriptions of his works with a solemn or tragic character. Its musical distinctiveness lies in Bach's masterly counterpoint and his ability to convey deep emotion through intricate musical structures.
Requires exceptional control over multiple independent voices and the ability to shape the harmonic progression expressively.
Actus Tragicus is rated Henle level 7 of 9 — late advanced repertoire, roughly ABRSM grade 8 and above. In the RCM system it corresponds to about level 10.
You should be comfortable at Henle level 7 — meaning you can already play level 6–7 pieces cleanly. Learning it one level early is possible as a stretch piece, but more than that usually leads to months of frustration.
A typical performance of Actus Tragicus lasts about 5 minutes.
Actus Tragicus is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.