Theodore Oesten's 'Bluettes de l'opéra' Op. 78 is a collection of salon pieces based on popular operatic melodies. They are characterized by their accessible arrangements and light, decorative pianistic textures.
Demands excellent technical command, including rapid scales, arpeggios, and precise articulation.
Bluettes de l'opéra (Op.78) is rated Henle level 5 of 9 — late intermediate repertoire, roughly ABRSM grades 6–7. In the RCM system it corresponds to about level 5.
You should be comfortable at Henle level 5 — meaning you can already play level 4–5 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 Bluettes de l'opéra (Op.78) lasts about 4 minutes.
Bluettes de l'opéra (Op.78) is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.