I have one hard rule about lyric writing: Use the Singular form over the Plural in every instance. “Boy” is better than “Boys” and “Snake” is better than “Snakes” and “Love” is better than “Loves.”
The reason for that rule is simple: The Plural “S” sound is one of the
worst and nasty sounds you can sing because no matter how you phrase it,
or intone it, an “S” sings like a “Hiss” and it hurts your ears.
Many of the composers I’ve worked with over the years look at me like I’m insane for
demanding the Singular use over the Plural — but my ears don’t lie,
and, unlike others, I am cursed with natural SuperHearing — and that means I know my “Hisses” when I hear them!
As well, when it comes time to record in studio, removing the “Hissing” from the lyric will make your audio recording engineer love you even
more.
Thanks for the good word, David. Singular of course starts with an s!
Perhaps if one were writing a musical with Skeletor from the He-Man universe, it would behoove one to include plurals — Skeletor was all about hissing! 
Ha! Words that start with “S” are not so bad — it’s the “S” at the end that hisses!