Vocaloid in Amestris Book #1 (VocaloidxFullmetal Alchemist crossover fanfiction)
Vocaloid 8 is performing Twilight NighT when Kaito, Rin, and Len get sucked into the Gate of Truth. They all are scattered around Amestris and Ed and Al have to to help them get home. (There will be a sequel for this! I have everything already planned.)