Facile
Easy, effortless.
What it means
Facile means “easy, effortless” and calls for a performance without visible effort. The music should flow as if it cost nothing — even when the passage is technically demanding.
The marking thus concerns the impression, not the degree of difficulty. It designates no relief for the player but a goal of shaping: effort should not become audible.
In addition, the word is met in titles and collections, where it actually means the difficulty — pieces “facile” are then easy to play. Which meaning applies follows from the place: above the staff, a performance instruction; in the title, an indication of the degree of difficulty.
Related is leggero, which means lightness in the sense of weightlessness.
In the notation
The word is written in italics above the staff, usually after a tempo word, and applies until a new marking. It is often found over runs, figures, and accompaniment patterns that should sound even and carefree.
Musical use
The marking is used in sections whose appeal lies in carefreeness: in variations of cheerful character, in playful middle sections, in passages that should seem light despite a high density of notes. In the piano and chamber-music literature it is widespread.
As a title, facile designates a technically easy piece: Mozart's Piano Sonata in C major, K. 545 (1788), bears the nickname Sonata facile; Mozart himself called it in his catalogue "a little piano sonata for beginners".
Performance practice
Keep your movements small and loose; lightness in the sound arises from looseness in the body. Take back the dynamics and avoid heavy accents. Choose the tempo so that all the notes succeed effortlessly — a passage at the limit never sounds light. And work on evenness: irregular figures betray effort at once.