A Dictionary of Music and Musicians/Bass Clef
BASS CLEF. The well-known mark of the bass clef, 
is a modification of the letter F, which has in the course of centuries arrived at its present shape, in the same way that the G and C have altered their forms.
The early sub-division of the graver male voices is attested by the variety of positions on the stave occupied by the bass or F clef. Since the beginning of the 18th century this clef (for whatever variety of bass voice) has occupied the fourth line exclusively. Up to that period its occasional position on the third line 
indicated that the music following it was for the baryton voice; the stave so initiated being called the baryton stave. At a still earlier epoch the bass clef was sometimes placed on the fifth line, 
. This basso profondo stave, which makes room for two more notes below than can be placed on the bass stave proper, is used (among others) by L. Lossius in his 'Psalmodia' (Wittenbach, 1579), and more recently by Praetorius in his 'Cantiones Sacrae' (Hamburg, 1622). It does not seem however at any time to have met with general favour. On the other hand, the baryton stave was much employed, not only for choral music, but for solos, up to the beginning of the last century. Some of Purcell's songs (e. g. 'Let the dreadful engines') in the 'Orpheus Britannicus' are written upon it, and with reason, for it takes in, with the aid of a single leger-line, the entire compass employed, from the lower A to the upper F. [ Clef.]
[ J. H. ]