Sentence:  The bass and treble clefs combined, include all the sounds belonging to our musical <WSD>system</WSD>, as they appear on a 6½-octave pianoforte, extending from C C C in the bass to F in altissimo. 
Meaning of the word marked with <WSD> tags:  A collection of organized things; a whole composed of relationships among its members. (from early 17th c.)