The traditional song is actually "Las Mañanitas," a folk song often performed by Mariachis. It is significantly longer and focuses on the beauty of the morning the person was born.
It is common to sing the "Cumpleaños Feliz" followed immediately by a fast-paced, rhythmic song known as "Ay, qué noche tan preciosa" (Oh, what a beautiful night). feliz_cumpleanos_original_version_en_espanol
In many Spanish-speaking cultures, particularly Mexico, the song ends with the "Mordisco." After singing, guests chant "¡Mordida, mordida!" and the birthday person must take a bite directly from the cake without using their hands (often resulting in their face being pushed into the frosting). The traditional song is actually "Las Mañanitas," a