 All of the regular cast performed their own vocals , although two actors were given minimal singing at their request . " Once More , with Feeling " is the most technically complex episode in the series , as extra voice and dance training for the cast was interspersed with the production of four other Buffy episodes . It was Joss Whedon 's first attempt at writing music , and different styles — from 1950s sitcom theme music to rock opera — express the characters ' secrets in specific ways . The episode was well received critically upon airing , specifically for containing the humor and wit to which fans had become accustomed . The musical format allowed characters to stay true to their natures while they struggled to overcome deceit and miscommunication , fitting with the sixth season 's themes of growing up and facing adult responsibilities . It is considered one of the most effective and popular episodes of the series , and — prior to a financial dispute in 2007 — was shown in theaters with the audience invited to sing along . 
