The page is forgiving. The vocal is not.
A line you wrote in a notes app at midnight may sit politely on the screen and then refuse to leave the singer's mouth in any pleasing way. The reasons are almost always the same β and once you notice them, you can fix them before the model ever has to attempt them.
Consonant clusters fight the breath
"Strict scripts" is fine to read. It is hostile to sing. Three consonants stacked between vowels force the singer to either rush or break the line into syllables that nobody will hear cleanly. If a line has a cluster that you yourself stumble over while reading it aloud, the model will stumble too.
Long vowels carry; short vowels skip
Open vowels (long o, long a, long e) hold the note. Short vowels skip past it. Lines that need to land β chorus hooks, title drops β should end on an open vowel. Lines that need to propel β verse setups, bridge transitions β can end on shorter vowels because momentum, not weight, is the goal.
Read it before you generate it
The fastest editor for AI-generated lyrics is your own voice. Read the verse out loud at the tempo you intend the song to live at. Any line that you reach for breath in the middle of, or have to slow down to articulate, is a line the singer will also struggle with. Cut it or rewrite it before you commit to the take.
When to let the model break the rule
Sometimes the wrong vowel is the right choice β the closed sound that makes a sad line feel even more closed off. Skill is not about following the rule; it is about knowing when you are breaking it on purpose and when you broke it because you were tired.