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, esp. 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.

in unison

in perfect accord; corresponding exactly

My feelings on the subject are in unison with yours.

noun

discord , disharmony

noun

accord , accordance , agreement , alliance , community , concert , concord , concordance , conjunction , consent , consonance , cooperation , federation , league , reciprocity , sympathy , unanimity , union , unity , concordant , consonant , harmony , together