A tone information processing apparatus comprising: a tone information acquisition section (1, S1, S2; S42) configured to acquire tone information indicative of a tone having a pitch element; and a chord information acquisition section (1, S11, S12; S46) configured to acquire chord information designating a chord, characterized in that said tone information processing apparatus further comprises: a determination section (1, S3, S21 - S23, S24, S36; S47) configured to determine whether one tone indicated by the tone information, acquired by said tone information acquisition section, has such a pitch variation that a pitch of the tone continuously varies at least from a first note pitch to a second note pitch, different from the first note pitch, for a particular time period within a sounding time period of the tone; and a pitch conversion section (1, S25, S27, S28, S29; S48, S50, S51, S52) configured to convert a pitch of the acquired tone information on the basis of a predetermined pitch conversion rule and the chord designated by the chord information acquired by said chord information acquisition section, wherein, when it is determined that the one tone indicated by the tone information has the pitch variation varying continuously at least from the first note pitch to the second note pitch, said pitch conversion section determines at least a first target note pitch corresponding to the first note pitch and a second target note pitch corresponding to the second note pitch independently of each other on the basis of the predetermined pitch conversion rule and the chord designated by the acquired chord information so that each of the determined target note pitches matches the chord designated by the acquired chord information, and converts at least the first note pitch and the second note pitch to the determined first and second target note pitches respectively. a tone information acquisition section (1, S1, S2; S42) configured to acquire tone information indicative of a tone having a pitch element; and a chord information acquisition section (1, S11, S12; S46) configured to acquire chord information designating a chord, characterized in that said tone information processing apparatus further comprises: a determination section (1, S3, S21 - S23, S24, S36; S47) configured to determine whether one tone indicated by the tone information, acquired by said tone information acquisition section, has such a pitch variation that a pitch of the tone continuously varies at least from a first note pitch to a second note pitch, different from the first note pitch, for a particular time period within a sounding time period of the tone; and a pitch conversion section (1, S25, S27, S28, S29; S48, S50, S51, S52) configured to convert a pitch of the acquired tone information on the basis of a predetermined pitch conversion rule and the chord designated by the chord information acquired by said chord information acquisition section, wherein, when it is determined that the one tone indicated by the tone information has the pitch variation varying continuously at least from the first note pitch to the second note pitch, said pitch conversion section determines at least a first target note pitch corresponding to the first note pitch and a second target note pitch corresponding to the second note pitch independently of each other on the basis of the predetermined pitch conversion rule and the chord designated by the acquired chord information so that each of the determined target note pitches matches the chord designated by the acquired chord information, and converts at least the first note pitch and the second note pitch to the determined first and second target note pitches respectively. a determination section (1, S3, S21 - S23, S24, S36; S47) configured to determine whether one tone indicated by the tone information, acquired by said tone information acquisition section, has such a pitch variation that a pitch of the tone continuously varies at least from a first note pitch to a second note pitch, different from the first note pitch, for a particular time period within a sounding time period of the tone; and a pitch conversion section (1, S25, S27, S28, S29; S48, S50, S51, S52) configured to convert a pitch of the acquired tone information on the basis of a predetermined pitch conversion rule and the chord designated by the chord information acquired by said chord information acquisition section, wherein, when it is determined that the one tone indicated by the tone information has the pitch variation varying continuously at least from the first note pitch to the second note pitch, said pitch conversion section determines at least a first target note pitch corresponding to the first note pitch and a second target note pitch corresponding to the second note pitch independently of each other on the basis of the predetermined pitch conversion rule and the chord designated by the acquired chord information so that each of the determined target note pitches matches the chord designated by the acquired chord information, and converts at least the first note pitch and the second note pitch to the determined first and second target note pitches respectively.