The anthem, again

Years later, another Grand Prix at the same racetrack, someone else singing the anthem, another live broadcast. This time the sound technician tested everything four times. Halfway through the preparations, in a forgotten box of parts in the pit garages, a very old earpiece turned up, and promptly disappeared again. Nine people and an earpiece, one per row and one per column. Nothing is handed to you on a plate: you'll need more than one hypothesis to get to the end.

Suspects

• Alcides, the sound technician: He still works at the racetrack. He tested the sound four times, and on the fourth asked everyone to sing quietly.
• Brígida, the broadcast director: She put one technician solely on watching the audio delay. She says never again half a second.
• Cristóvão, the bike mechanic: He opened the box of small parts for the first time in years. He found washers, screws and something that wasn't his.
• Dulcineia, the executive producer: She started as the broadcast intern in 2022. Now she runs the broadcast and still looks at her phone, but for good reasons.
• Edmundo, the guest singer: He's singing the anthem. He asked for the new earpiece, the old one and a spare.
• Francelina, the fan who was there in 2022: She came to see if it would go right this time. She brought earplugs, just in case.
• Galvão, the motorsport journalist: He writes the race report and one line about the anthem, like years ago. The line still gets more readers.
• Hipólito, the track marshal: He waves the flags. For the anthem, this time, he knows which one: none.
• Iracema, the podium hostess: She gets the bottles ready for the podium. She says they're only opened after the anthem, to avoid confusion.