Concone 50 is used as a teaching material for most of the beginning students of vocal music in Japan. Vocalizes such as those by Concone, with no specific languages accompanying them, can effectively help students to develop skills of connecting notes to form a melody line before they start singing pieces with lyrics. Such skills are essential for singers, no matter which language they may sing in. Professor Emeritus Ryosuke Hatanaka, editor of Zen-On Music's Concone 50 Lessons, writes in its preface that usage of Concone 50 can be categorized into three, namely using it (1) in solfeggio lessons; (2) for genuine practice in vocalization; and (3) for learning artistic expression of melodies. He then argues that it is impossible to master all the three categories in a single go-through; his belief, to put it in extreme terms, is that Concone 50 is a lifetime textbook for students of vocal music; even if they focus only on selected basics, it should be learned over at least three years. However, it is not feasible in the teacher training program at Hiroshima University to cover Concone 50 completely, nor to spend three years on learning it. With the time constraint as it is, using only selected pieces in solfeggio lessons, as suggested in above (1), would be more realistic. For the purpose of making such selections more efficient, this study explores a way to evaluate each piece in Concone 50 by certain numerical figures as opposed to the conventional, subjective judgment. Among the various factors that constitute music, this study focuses solely on degrees between notes, considering the fact that the pieces in Chorubungen, the most common material that precedes Concone 50, are introduced in the increasing order of degrees.