If you’re the sort of person who remains locked in a private, perpetual tug of war over whether the greatest singer this country’s ever known is Aretha Franklin or Whitney Houston, perhaps you’re also the sort of person who then spares a thought for Whitney’s mother, Cissy. Cissy Houston died at 91 on Monday, and she could sing, too. Let me try that again: Cissy Houston sang, first with the clarity of something just Windexed then, later, with a tone that acquired some protective, matured texture, some bark.

This thought we “who’s the greatest” vacillators spare for Miss Cissy stems from outrageous misfortune: yes, the unimaginable tragedy of losing a daughter the way she lost Whitney and then losing her daughter’s daughter, Bobbi Kristina Brown, almost exactly the same way; but also being Whitney’s mother, plus Dionne Warwick’s aunt and a cousin of opera legend Leontyne Price, in addition to one of Aretha’s homies. How could a member of that bloodline not be in pursuit of music that could garner the sort of acclaim and career they experienced? But Cissy never found it.

Warwick cast her spells with a chardonnay glimmer, singing with low-pulse seduction that had some tooth. Whitney was a fighter jet who could dance Balanchine and Ailey. Miss Cissy had power and range and a knack for put-you-in-your-place phrasing, whether the subject was the Man Upstairs or the man in her bed. But what Cissy lacked was good luck — never had original songs as top-shelf as her niece’s or as humongous as her daughter’s.

After a few years of significant group work with the Sweet Inspirations and an underrated solo album in 1970, she was trying disco (the “Think It Over” album, from 1978) and, the year before, choir-robed R&B on “Cissy Houston,” an album studded with covers that for all its heat and arched eyebrows could easily have been titled “Mavis Staples,” too. But look: Cissy is really feeling the tunes on that LP, reshaping, reliving, husking them. There’s weariness and want, some funk. She sounds like a woman who just walked in the front door after nine hours on her feet, who faintly remembers what being swept off them was like.

Her career began perched at an upper register whose uncanny inheritor is obviously her daughter — the soprano punch-ups and dessert-for-dinner runs. But by 1977, up there, Cissy was often at her ceiling. You can sometimes hear muscle in her climbs, the labor of singing. Some voices can’t wait to get to the skies of a chorus. The alto Miss Cissy embraced seemed to luxuriate in the verses. She always sounded as if the first-floor was as good as the penthouse.

There are a couple of killer reconsiderations — of Elton John’s “Your Song” and “Tomorrow,” the mood elevator from “Annie.” In 1977, that one was brand-new, so not yet a bright-side cliché. Besides, when a singer like Cissy Houston does it, you’re not seeing redheaded urchins. When a singer like her does it, you’re seeing tour buses and no-star hotels and hearing perseverance and straight-talk homesickness. You’re listening to someone accept how a just-Windexed voice had become ever so stained, how to work with that. Not for nothing, she remained instrumental to America’s gospel scene, and she did it from Newark, New Jersey.

By the 1980s, the personal recordings paused while she committed herself to arranging a launchpad for Whitney and helping chart the course of her apogee. The Whitney Elizabeth Houston annalists and academes debate what Cissy did and didn’t do for her daughter, with respect to, for starters, what kind of music to make. Tell-all books and gossipy, speculative movies have splatter-painted Houston family portraits while, for decades, discussion forums have been doubling as symposia. But no matter where the Houstonographers land on this family’s history and dynamics, Cissy remains an intriguingly consequential biological nexus of vocal might.

As one of these pitiful “who’s the greatest” people who has also spared a thought or two for Miss Cissy, I often think about the time she most ethereally deployed that voice. I always savored it, because it could be one of the greatest notes ever hit in a recording. The group singing Houston did with the Sweet Inspirations included backing other acts — Van Morrison, Elvis Presley, Wilson Pickett, Jimi Hendrix, Dusty Springfield. But the Inspirations extended their steadiest support to Franklin. And Cissy’s apex on their songs together occurred in 1968, on Franklin’s album “Lady Soul.” That’s the one with “Chain of Fools” and “(You Make Me Feel Like) a Natural Woman.” It’s the closing track, though — “Ain’t No Way” — that’s always induced paralysis. Aretha’s sister Carolyn Franklin wrote it, and it slowly burns and builds, an album marching toward its spectral fade out. Merely with Aretha, it’s a gorgeous chamber-like piece, a haunting way to end an already perfect album.

Then at about the 63rd second, this tremendous, vertiginously pitched sound rises up behind Aretha’s earthiness: a signal, a siren, a sun. This is Cissy Houston. And it’s not simply that she hits and holds the note for 13 seconds. It’s that she gives it shape and body. The note quivers. It aches. A vocalist friend of mine guesses she’s at a high C — the Himalayas, basically. But you don’t hear climbing, just elongation, luxuriation. The way Cissy has been recorded, it’s as if the note is a dream rising from Aretha’s unconscious. But it’s also as if someone’s lifted up a bell jar, studied what’s wafted out and gently replaced it. The note comes out, peaks, then sets. The clarity is so otherworldly that I used to forget a woman produced it and not a theremin.

“Ain’t No Way” last four minutes and 12 seconds. The jar gets lifted five times. Surely, the opera of that note rocked cousin Leontyne, too. It’s the only time I know that Aretha Franklin is making the second-most staggering sound on an Aretha Franklin record.

In 1983, Merv Griffin now famously invited a 19-year-old Whitney Houston to make her television debut. Cissy is at her side. They duet for a deftly arranged, high-energy medley. “Ain’t No Way” takes up a meaty chunk. The daughter does Aretha. The mother does herself. And it’s tempting to say outdoes, for The Note is still in her reach and therefore all of the grace, power and glory it conjures. Here, even on “Merv Griffin,” is a stirring, holy, redemptive sight that any “spare a thought for Cissy” person is welcome to interpret as revenge.