Electronic musical instrument with counter melody function

The electronic musical instrument is provided, in addition to usual tone producing circuitries associated with playing keys, with a chord designating circuit designating, according to key depression, a plurality of notes of that constitute a chord, a change detecting circuit for detecting a change in designated chord, a note selection circuit for selecting a note from among the designated notes according to a predetermined condition related to the preceeding selected note when the chord change is detected, and a musical tone forming circuit for forming musical tones of the selected notes. Succession of the selected notes constitute a counter line melody automatically established to meet the music being played on the instrument.