[2] Some of the guest vocalists and musicians that have been featured on Avantasia are Michael Kiske, Jørn Lande, Alice Cooper, Klaus Meine, Dee Snider, Hansi Kürsch, Jon Oliva, Biff Byford, Joe Lynn Turner, Tim "Ripper" Owens, Geoff Tate, Kai Hansen, Rudolf Schenker, Bruce Kulick, Sascha Paeth, Eric Singer, Bob Catley, Roy Khan, Russell Allen, Timo Tolkki, Rob Rock, David DeFeis, Andre Matos, Sharon den Adel, Floor Jansen, Ralf Scheepers, Marko Hietala, Arjen Anthony Lucassen, Henjo Richter, Markus Grosskopf, Jens Johansson, Eric Martin, Ronnie Atkins, Oliver Hartmann, Mille Petrozza, Candice Night and Amanda Somerville.

In Spring 1999, during Edguy's 'Theater of Salvation' tour, Tobias Sammet began to outline his ideas for a metal opera concept album featuring a number of guest musicians.

When the tour finished, he began collaborating with metal vocalists like Michael Kiske, Andre Matos, Kai Hansen, Rob Rock, David Defeis, Sharon den Adel, Bob Catley and Oliver Hartmann to record the project.

At this stage the core band consisted of four members, Sammet on keyboards, Henjo Richter on guitar, Markus Grosskopf on bass and Alex Holzwarth on drums.

[5] After the release of The Scarecrow, Tobias Sammet was invited to perform a headlining show at Wacken Open Air, an offer that producer/guitarist Sascha Paeth convinced him to accept.

The line-up for the short tour consisted of Tobias Sammet, Andre Matos, Jørn Lande, Kai Hansen, Bob Catley, Amanda Somerville, Cloudy Yang, Sascha Paeth, Oliver Hartmann, Robert Hunecke, Miro and Felix Bohnke (Edguy).

[7] The special guests included drummers Eric Singer, Alex Holzwarth and Felix Bohnke, guitarists Bruce Kulick and Oliver Hartmann, keyboardist Jens Johansson and vocalists Jørn Lande, Russell Allen, Michael Kiske, Bob Catley, Klaus Meine, Tim "Ripper" Owens, Jon Oliva, Andre Matos, Cloudy Yang and Ralf Zdiarstek.

[9] A 12 show tour of Europe, South America and Asia took place during December 2010, with the exception of one concert at the Wacken Open Air festival in August 2011.

After the worldwide success of the latest studio releases, an arena world tour that was sold out pretty much everywhere, collaborations with childhood heroes...I 'knew' that I had said everything I could possibly say in the name of Avantasia.

[16][17] The line-up for the tour consisted of vocalists Tobias Sammet, Michael Kiske, Ronnie Atkins, Eric Martin, Bob Catley, Thomas Rettke, Amanda Somerville and musicians Sascha Paeth, Oliver Hartmann, Miro, Andre Neygenfind and Felix Bohnke.

[26] On 10 October Nuclear Blast officially announced the new album Moonglow would be released on 15 February 2019, and would feature guest vocals by Jørn Lande, Geoff Tate, Ronnie Atkins, Hansi Kürsch, Bob Catley, Michael Kiske, Candice Night, Eric Martin and Mille Petrozza.

[27] Subsequently, the album was accompanied by the Moonglow World Tour 2019 consisting of 29 concerts across Europe, Australia, and the United States and South America taking place between March and June 2019.

[30] The album was released on 21 October 2022 under the title A Paranormal Evening with the Moonflower Society and featured guest vocals by Floor Jansen, Jørn Lande, Michael Kiske, Ralf Scheepers, Bob Catley, Geoff Tate, Eric Martin and Ronnie Atkins.