Having or indicating, equal tones, or tension.
Webster's Revised Unabridged Dictionary (1913), edited by Noah Porter. About
\i`so*ton"ic\ (?), a. [iso- + tonic.] having or indicating, equal tones, or tension.
system (mus.), a system consisting of intervals, in which each concord is alike tempered, and in which there are twelve equal semitones.