Abstract: Many variants with convertible notes appeared in Songbenyupian. The four note conversion modes are switching to variants of the same notes, to the homophone, to the characters with similar note (classified into 7 scales by sound similarity), and to the characters with different notes. Phonetic functions of notes are considered in most cases of the variants conversion, while some are not. Four reasons are concluded: to simplify the notes, to select a specific note in the analogy, to inherit the ancient notes which have phonetic effect, and to remain notes from the dialects or lost pronunciation.