I was onstage that fated night, Sept. 22, 2017, with my band Mashrou’ Leila. We’re an indie group from Beirut and have played across the Middle East and beyond for more than a decade now. Our Arabic lyrics tell stories of love, hope, loss, inequality and corruption, speaking to the ills that plague our region.

Performing onstage has given me my proudest memories. From where I usually stand, I look out at the sea of dreamers holding signs, waving flags, laughing, screaming and singing their hearts out. Collectively, we — band and fans — do what the Middle East’s leaders won’t: create a home for all of us. Class, race, sexuality, gender, politics and religion all fade away for two hours. Such a version of what the Arab world could be is a powerful rebuke and a threat to what the dictators, Islamists and sectarians have been offering us instead for decades.

Though we have performed at some of the most iconic venues across the globe, that concert in Cairo was our largest ever, with 35,000 people in attendance. To perform for so many in the soul of the Arab world, as Egypt is considered, was a milestone for us and a testament to that hunger for change.

Our band came together in 2008, in a series of late-night jam sessions in Lebanon. We were architecture students, thinking we’d build a better world through the houses, museums and cities we’d design. Instead, through our music and the people it brought together, we ended up building a community, one that transcends the tribal identities that have long held us back. What we do share is a belief in the possibilities of fairer, brighter and more resilient futures.

While I never met Ms. Hegazi, I feel I knew her. A photo from that night immortalizes her, the same one that would seal her fate when it went viral. She’s aloft on the shoulders of a friend, gloriously raising the rainbow flag; it almost gives her wings.

I visit her at that concert in my memories: Lights dimmed, an intimate and safe darkness transports us all to Marrikh, Arabic for Mars and the name of one of our songs. We performed it under the stars in Cairo to a constellation of swaying cellphone lights. I’ve also sought videos posted online of that night, shot from different angles with shaky cameras: pixelated dreams and noise-distorted recordings of the emotions of thousands.

At first, Ms. Hegazi’s picture was greeted online as a triumphant exclamation of pride. Within days, it was used to whip up public hysteria and justify a homophobic arrest campaign. The Egyptian government imprisoned and tortured Ms. Hegazi, and many others, mostly on the basis of their real or perceived sexual orientation or gender identity — as it has done for decades and continues to do.

That Ms. Hegazi felt safe enough to honor our music with her bravery is thrilling; that such a simple act forever altered and then ended her life brings me great sorrow. That plummet — from hope to despair — is familiar to anyone who dared to believe in the Arab Spring.

In those early days of hope, our band dedicated a video to the “generation of the revolution.” In 2011, we performed our first shows ever in the countries that led the Arab Spring, Tunisia and Egypt. We used our platform to amplify Arab women’s voices, played fund-raisers for Syrian refugees, campaigned for sustainable environmental projects and advocated L.G.B.T.Q. rights and sexual-health awareness. Our lead singer has always been open about his queerness. As we started touring the world, we met many inspiring queer Arab activists. Their courage and resilience taught me to be more at ease with my own sexual identity and queerness.

But the old guard quickly reasserted itself across the Middle East, answering the youthful uprisings with a brutal and oppressive counterrevolution.