[Problem] To provide an arpeggiator capable of creating a rich arpeggio performance that includes multiple pieces of performance information, and a program equipped with a function therefor. [Solution] When the key press mode for a sounding part is a chord, a synthesizer 1 acquires all note numbers from a remain table for the sounding part in a setting table 11e and stores all the note numbers in an Arp note memory 12b. This allows all the notes corresponding to the note numbers set in the remain table to be concurrently generated at the sounding time set in an Arp pattern. That is, an expressive arpeggio based on a chord made up of all the notes corresponding to the note numbers set in the remain table can be produced.