An adaptive chord-generating apparatus and method exactly generates chord data specified by a performer by an operation method according to the number of constituent notes of a chord inputted by a performer. To do this, the apparatus and method comprises a keyboard for receiving constituent notes of chord and melody, a memory where a chord search table is stored, a control portion for searching a chord search table of the memory according to a rule corresponding to the number of constituent notes inputted from the keyboard and generating chord data having a chord type and a pitch based on the searched data, and a sound source generator for generating a musical instrument sound signal having a predetermined pitch of chord corresponding to chord data supplied from the control portion.