clef(n = noun.communication) - a musical notation written on a staff indicating the pitch of the notes following it;
is a kind of musical notation
has particulars: g clef, treble clef, treble staff, bass clef, f clef, alto clef, viola clef, c clef, soprano clef, tenor clef

   A character used in musical notation to determine the position and pitch of the scale as represented on the staff. [1913 Webster]
" The clefs are three in number, called the C, F, and G clefs, and are probably corruptions or modifications of these letters. They indicate that the letters of absolute pitch belonging to the lines upon which they are placed, are respectively C, F, and G. The F or bass clef, and the G or treble clef, are fixed in their positions upon the staff. The C clef may have three positions. It may be placed upon the first or lower line of the staff, in which case it is called soprano clef, upon the third line, in which case it called alto clef, or upon the fourth line, in which case tenor clef. It rarely or never is placed upon the second line, except in ancient music. See other forms of C clef under C, 2." [1913 Webster]

clef, n. Mus. any of several symbols placed at the beginning of a staff, indicating the pitch of the notes written on it.

Etymology:
F f. L clavis key

N  concord, accord, harmony, symphony, homologue, agreement, sympathy, empathy, response, union, unison, unity, bonds of harmony, peace, unanimity, league, happy family, rapprochement, reunion, amity, alliance, entente cordiale, good understanding, conciliation, peacemaker, intercessor, mediator, concordant, congenial, agreeing, in accord, harmonious, united, cemented, banded together, allied, friendly, fraternal, conciliatory, at one with, of one mind, at peace, in still water, tranquil, with one voice, in concert with, hand in hand, on one's side, commune periculum concordiam parit, melody concord, melody, rhythm, measure, rhyme, pitch, timbre, intonation, tone, scale, gamut, diapason, diatonic chromatic scale, enharmonic scale, key, clef, chords, modulation, temperament, syncope, syncopation, preparation, suspension, resolution, staff, stave, line, space, brace, bar, rest, appoggiato, appoggiatura, acciaccatura, note, musical note, notes of a scale, sharp, flat, natural, high note, low note, interval, semitone, second, third, fourth, diatessaron, breve, semibreve, minim, crotchet, quaver, semiquaver, demisemiquaver, hemidemisemiquaver, sustained note, drone, burden, tonic, key note, leading note, fundamental note, supertonic, mediant, dominant, submediant, subdominant, octave, tetrachord, major key, minor key, major scale, minor scale, major mode, minor mode, passage, phrase, concord, harmony, emmeleia, unison, unisonance, chime, homophony, euphony, euphonism, tonality, consonance, consent, part, harmony, harmonics, thorough-bass, fundamental-bass, counterpoint, faburden, piece of music, composer, harmonist, contrapuntist (musician), harmonious, harmonical, in concord, in tune, in concert, unisonant, concentual, symphonizing, isotonic, homophonous, assonant, ariose, consonant, measured, rhythmical, diatonic, chromatic, enharmonic, melodious, musical, melic, tuneful, tunable, sweet, dulcet, canorous, mellow, mellifluous, soft, clear, clear as a bell, silvery, euphonious, euphonic, euphonical, symphonious, enchanting fine-toned, full-toned, silver-toned, harmoniously, in harmony, as one, the hidden soul of harmony.

alto clef, bass clef, c clef, f clef, g clef, roman a clef, soprano clef, tenor clef, treble clef, viola clef