The ABAC song form is similar to the ABAB song form. It starts with an 8-bar A section, then an 8-bar B section. However, in ABAC song form example, the structure returns to A section and is followed by C section instead of B.
The initial few bars of C section sound similar to B section, but in ABAC song form, the melody turns into something completely different.
This song form is very popular in stage musicals and movie theme music. One example of this song form is the composition ‘Moon River’ by the celebrated musician Andy Williams.
The C section in the ABAC song form begins off melodically, and lyrically it is similar to B section in ABAB song form. But the melody in the ABAC song form drastically changes from the ABAB song form after the C section, and the lyrics go off in a new direction.