It can also be used, more specifically, to indicate that a passage of music was to be played exactly as written, or only by the specified instrument, without changes or omissions.
The word is borrowed from Italian (an adjective meaning mandatory; from Latin obligatus p.p.
[4] Obbligato includes the idea of independence, as in C. P. E. Bach's 1780 Symphonies mit zwölf obligaten Stimmen (with twelve obbligato parts) by which Bach was referring to the independent woodwind parts he was using for the first time.
[5] A difficult passage in a concerto might be furnished by the editor with an easier alternative called the obbligato (but more commonly and correctly termed an ossia); or a work may have a part for one or more solo instruments, marked obbligato, that is decorative rather than essential; the piece is complete and can be performed without the added part.
One contemporary usage, however, is that by Erik Satie in the third movement of Embryons desséchés (Desiccated Embryos), where the obbligato consists of around twenty F-major chords played at fortissimo (this is satirising Beethoven's symphonic style).