What is In unison?
In unison definition and meaning on Dictionary terms:
coincidence in pitch of two or more musical tones, voices, etc.
the musical interval of a perfect prime.
the performance of musical parts at the same pitch or at the octave.
a sounding together in octaves, especially of male and female voices or of higher and lower instruments of the same class.
a process in which all elements behave in the same way at the same time; simultaneous or synchronous parallel action: to march in unison.