It’s our beloved bedtime ritual: In the dark of my son’s room, at the edge of his small bed, I sing him to sleep every night. From the day he was born, I’ve been lulling him off to dreamland by warble-whispering the random anthems filed in my musical memory. Lullabies. Folk tunes. Soulless pop songs from the 1980s.

I love our routine so much, love sending my custom soundtrack — like a mommy mix-tape — resonating through his subconscious as he slumbers. It relaxes him. It relaxes me. It’s achingly peaceful.

Until the vulgarities start flying.

You see, he’s a musical child. Sings with conviction, dances with abandon, and hopes to play the tuba someday … when he’s bigger than one. The kid’s got perfect pitch, impeccable rhythm, and — herein lies the problem — uncanny recall for every lyric he’s ever heard. Ever.

So if he recognizes a song during our nightly tunefest, he sings along boisterously — negating the whole “lulling” objective. If I “sshhh” him in that gentle-but-I’m-dead-serious way that only mothers can, he begins dancing horizontally to the ditty, thumping its backbeat on the pillow, making James Brown faces and kicking his legs in spastic homage to a mosh pit he clearly visited in a former life.

Don’t get me wrong; I love to groove with my son. I break-dance with him on Saturday mornings when my caffeine’s kicked in and the unscheduled day stretches out before us like the Soul Train Line.

But when the moon’s high, my eyelids are low, and there’s an episode of Entourage waiting for me on TiVo, I want the kid silent, still, and slack-jawed. Is that so wrong?

This means that in order to sufficiently bore, I mean soothe, him to sleep, I have to sing a song he doesn’t know — a new song — almost every night. Yes, really. Which is how I wound up crooning tunes entirely inappropriate for a 5-year-old.

One can only delve so deep into the American pop music catalog before one bumps (and, dear god, grinds) against sex, drugs, and foul language. And that’s before Entourage even starts.

Oh, sure, things were fine during the “Tura Lura Lura” and “Iko Iko” days (nonsense words have a Lunesta-like effect on restless wee ones). Tin Pan Alley oldies and Broadway show tunes proved no problem. But when I whipped out “King of the Road,” I hit trouble. Helping himself to cash boxes left unlocked? Puffing from stogies found on the ground? What sort of unsavory dreams would such grifting inspire?

I vowed to select more wholesome songs and was halfway through Simon & Garfunkel’s dulcet “The Boxer” when my son groggily inquired about the whores on Seventh Avenue. Oops. Billy Joel proved no better: “Only the good die young” is a phrase likely to make a kindergartner terrified, or else very, very naughty.

Era after era, Billboard chart after Billboard chart, my personal songbook revealed itself to be unrelentingly unrelaxing — at least to me. I’ve accidentally stepped in “funky (dung)” during Steve Miller’s “Jet Airliner” and clumsily buzzed around a sex-toy reference midway through Jason Mraz’s “Geek in the Pink”; it’s like reading him “Go the (Bleep) to Sleep” as a bedtime story. The offending words escape my lips before my end-of-day-weary mind can stop them, and then seem to hang menacingly in the air just over my son’s perfect little ears, leaving me to wonder if all songs are crude — or just the ones I enjoy.

Last night, nearing the utter bottom of my musical reservoir, I gave up and wailed “Let’s Get It On” from start to finish, complete with breathless grunts and not-remotely-nimble innuendo. Sigh. Maybe it’s time to hang up my microphone and invest in a tuba.