Douglas R. Docker: live (2019-2020), "The Mystic Technocracy - Season 2: The Age of Entropy" (2021)

Tony Franklin: "The Mystic Technocracy - Season 1: The Age of Ignorance" (2012)

Giorgio Novarino: "The Mystic Technocracy - Season 2: The Age of Entropy" bonus track (2021)

Luca Pisu: "The Mystic Technocracy - Season 2: The Age of Entropy" (2021)

Anna Portalupi: live (2013), "The Heisenberg Diaries - Book A: Sounds of Future Past" (2016)

Roby Salvai: "The Mystic Technocracy - Season 2: The Age of Entropy" (2021)

Celeste Veglia: live (2013)

Guthrie Govan: "The Mystic Technocracy - Season 1: The Age of Ignorance" (2012)

Joel Hoekstra: "The Mystic Technocracy - Season 2: The Age of Entropy" (2021)

Yasi Hofer: "The Heisenberg Diaries - Book A: Sounds of Future Past" (2016)

Luigi Iamundo: "The Mystic Technocracy - Season 2: The Age of Entropy" bonus track (2021)

Michael Infantino (Black Swan student special guest): live (2013)

Mio Jäger: "The Heisenberg Diaries - Book A: Sounds of Future Past" (2016), "The Mystic Technocracy - Season 2: The Age of Entropy" (2021)

Gianluca Nardelotto: live (2019-2020)

Sascha Paeth: "The Mystic Technocracy - Season 2: The Age of Entropy" (2021)

Davide Ronfetto: live (2013)

Nita Strauss: "The Heisenberg Diaries - Book A: Sounds of Future Past" (2016)

Toni Urzì: live (2019-2020), "The Mystic Technocracy - Season 2: The Age of Entropy" (2021)

Celeste Veglia (Black Swan student special guest): live (2013)

Jeff Watson: "The Mystic Technocracy - Season 1: The Age of Ignorance" (2012)

Douglas R. Docker: all albums (2008 - present day), live (2013)

Paolo Gambino: live (2019-2020)

Donald D. Docker: alto & tenor sax, clarinet on "The Mystic Technocracy - Season 1: The Age of Ignorance" (2012)

Elizabeth Andrews: "The Mystic Technocracy - Season 2: The Age of Entropy" (2021)

Cinzia Carraturo (Black Swan student special guest): lead and backing vocals live (2013)

Mattia Casabona: growl and scream vocals live (2020)

Eleonora Comba (Black Swan student special guest): lead and backing vocals live (2013)

Douglas R. Docker: lead and backing vocals, spoken voice on all albums and live (2008 - now)

Donald D. Docker: spoken voice on "The Mystic Technocracy - Season 1: The Age of Ignorance" (2012)

Göran Edman: lead and backing vocals, spoken voice on "The Mystic Technocracy - Season 1: The Age of Ignorance" (2012)

Kelly Massenz (Black Swan student special guest): lead and backing vocals live (2013)

Giacomo Mazzaro (Black Swan student special guest): backing vocals live (2013)

Tony Mills: lead and backing vocals on "The Mystic Technocracy - Season 1: The Age of Ignorance" (2012)

Serena Moine: lead and backing vocals on "The Mystic Technocracy - Season 2: The Age of Entropy" (2021)

Lucia Partiti (Black Swan student special guest): backing vocals live (2013)

John Payne: lead and backing vocals on "The Mystic Technocracy - Season 1: The Age of Ignorance" (2012)

Anna Petracca: lead and backing vocals live (2013, 2019-2020), "The Mystic Technocracy - Season 2: The Age of Entropy" (2021)

Valentina Procopio: lead and backing vocals on "The Heisenberg Diaries - Book A: Sounds of Future Past" (2016), live (2018), "The Mystic Technocracy - Season 2: The Age of Entropy" (2021)

Andrea Rampa: lead and backing vocals live (2013, 2019-2020)

Janthana Rodjakkhen: spoken voice on "The Mystic Technocracy - Season 1: The Age of Ignorance" (2012)

Elize Ryd: lead vocals on "The Heisenberg Diaries - Book A: Sounds of Future Past" (2016)

Jessica Scardina: lead and backing vocals live (2019-2020)

Amanda Somerville: lead and backing vocals on "The Mystic Technocracy - Season 1: The Age of Ignorance" (2012), "The Heisenberg Diaries - Book A: Sounds of Future Past" (2016) and "The Mystic Technocracy - Season 2: The Age of Entropy" (2021)

Anneke Van Giersbergen: lead vocals on "The Mystic Technocracy - Season 2: The Age of Entropy" (2021)