An automatic composition apparatus includes a processing unit. The processing unit performs a receiving process of receiving a phrase including a plurality of note data items as a received motif and receiving a type of the phrase, a retrieving process of retrieving a phrase set from a phrase set database and a melody generating process of generating a melody based on the retrieved phrase set. The phrase set includes phrases having the same type as the received type and having relatively high matching levels for the received motif. The phrase set database stores a plurality of phrase sets each of which is a combination of a plurality of phrases of different types.