In the Nanoha franchise, the term Sound Stage(サウンドステージSaundo Stēji) refers to an audio drama CD. These are usually published as supplements to the anime seasons and are considered their "extra" episodes. They are equally canonical in the continuity of the respective series as regular episodes.
Set two years before the main series, this Sound Stage describes Fate's life before coming to Earth. Presea's familiar Rinis successfully tutors her and creates Bardiche. She also helps Fate with creating her own familiar, Arf. When Fate's training is complete, Rinis dissipates and Presea sends Fate after the Jewel Seeds.
A peek into family scenes in Harlaown and Takamachi families. The Forwards take to the skies to engage some Gadget Drones and bond. Lindy and Arf help resolve some problems between Fate and her Forwards. The Yagamis visit the Saint Church for a checkup and reminiscing about the old times.
The Riot Force 6 is transferring to the Arthra following the Numbers' attack on the Long Arch and are resting, recovering and preparing for the next challenge. Meanwhile Lutecia, Zest and Agito discuss Agito's past and her potential past Lord that she can no longer remember. Numbers, too, are recuperating and discuss their recent successes and failures and their backgrounds. Yuuno is helping RF6 by deciphering Carim's prophecy and cheering up Nanoha. Meanwhile, at the Yagami residence, Rein starts having dreams that bring up memories of Reinforce's involvement in the old Belkan wars and her hope for a better future.
Account of the final days of Riot Force 6 and thoughts on the future of both the officers and the young Forwards and their former opponents, the Numbers.
Three years after the JS Incident, Midchilda is struck by a spree of mysterious killings associated with yet another piece of dangerous Ancient Belkan legacy. The former Forwards of Riot Force 6 and the reformed Numbers join forces once again to stop this new threat, the Mariage, and its mysterious creator, the Dark King Ixpellia.