Bachianas Brasileiras No. 1 is the earliest in the series, originally for cello ensemble, but widely known in its piano transcription. It's characterized by its lush harmonies, flowing melodic lines, and a deep sense of Brazilian atmosphere, evoking the sounds of the rainforest.
Requires a singing tone and mastery of legato phrasing to convey the piece's rich harmonic language and melodic beauty.
Bachianas Brasileiras No. 1 is rated Henle level 5 of 9 — late intermediate repertoire, roughly ABRSM grades 6–7.
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.
Bachianas Brasileiras No. 1 is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.