“’Falling in love is so bittersweet,’ Whitney Houston wails. ‘This love is strong. Why do I feel weak?’ But falling in love doesn’t sound bittersweet, and Whitney Houston doesn’t sound the slightest bit weak,” (Stereogum). “Instead, she sounds like an volcano of joy, an unstoppable natural force of pure exhilaration. At least on paper, ‘How Will I Know’ (1985), Houston’s second chart-topper, is a song about uncertainty — about feeling your way around in the dark, trying to understand if someone else feels the same way you do. But that’s not how Houston sings it. Instead, Houston sings ‘How Will I Know’ as if she can barely contain the excitement that comes along with that uncertainty. She sings it like she already knows.
… Houston just goes off on this thing. It’s amazing to behold. Houston sells the emotion of the song, sounding like she’s utterly caught up in this dazzling, exciting, world-ending crush. She also nails every little melodic turn … But even in the context of a song as fast and bubbly as this one, you can still hear the power and control in her voice. There’s a lot of gospel in her delivery, in the unearthly joyous yelps and whoops and out-of-nowhere high notes. (There’s a whole lot of gospel in those backing vocals, too.) And while Houston never fully cuts loose on ‘How Will I Know,’ she also keeps her abilities in full view. You can hear that voice bursting its way out of the song, ready to dive and curl and soar. The biggest note — the ‘how will I knoooooow‘ just as the sax solo kicks in — is enough to give a motherfucker goosebumps.”
After a start in Gb major, the bridge consistently builds via a repetitive short melody fragment (“If he loves me / If he loves me not”) layered over harmonies that shift with each iteration of the lyric (3:07 – 3:31). As the sax solo kicks in, there’s a massive downward jump to Eb major — but there’s no accompanying deflation in energy, as Whitney’s vocal moves decisively up at that point, not down. In the closing bars, however, the return of the chorus clearly demonstrates the lower key.