John Weeks Moore, Complete Encyclopaedia of Music… (1880)
“ Alla breve (I.) is the proper designation of the time of a piece of music, in which the breve is equal to a semibreve in time ; and is to be played in a movement of twice the usual rapidity ; so that a breve is played as fast as a semibreve, a semibreve as fast as a minim, and so on. ”
