Telemann's 'Old Adam, You Must Die' is a deeply expressive aria, likely a movement from a sacred work or cantata. Its title suggests a theme of mortality and spiritual reckoning, rendered with Baroque pathos.
Practice precise ornamentation and controlled dynamic shaping to enhance the expressive depth.
Alter Adam, du mußt sterben, TWV 1:90a is rated Henle level 4 of 9 — intermediate repertoire, roughly ABRSM grades 5–6. In the RCM system it corresponds to about level 7.
You should be comfortable at Henle level 4 — meaning you can already play level 3–4 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 Alter Adam, du mußt sterben, TWV 1:90a lasts about 3 minutes.
Alter Adam, du mußt sterben, TWV 1:90a is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.