Question: Are both Tobias Sammet and Minoru Niihara in heavy metal bands?

Context articles: Rob Rock
Monuments (Edguy album)
Dezperadoz
Tobias Sammet
Holy Hell (Rob Rock album)
Sly (band)
Canadian heavy metal
Minoru Niihara
Tobias Exxel
On the Prowl (album)

Robert "Rob" Rock is an American heavy metal singer-songwriter, best known as the longtime frontman of Impellitteri, a position he has held from 1987 to 1988, 1992 to 2000, and now from 2008 to the present day.
 Rock has also released five albums as a solo artist, and performed with a number of other notable artists, including M.A.R.S., Joshua, Tobias Sammet, Axel Rudi Pell and Warrior.
Monuments is a compilation album by the German power metal band Edguy, released on 14 July 2017.
 The album was released as a two-CD/DVD package including 22 old songs, five new songs, and a previously unreleased song from the original "Savage Poetry" recordings back in 1995.
 The package also includes a two-hour DVD and a photobook.
 Frontman Tobias Sammet wrote two of the new songs on his own, while guitarists Jens Ludwig, Dirk Sauer and bassist Tobias Exxel co-wrote each of the other three.
Dezperadoz (formerly "Desperados") is a German "Western-metal" band and is the side-project of Tom Angelripper's guitarist Alex Kraft.
 The band plays heavy metal music that is heavily influenced by the soundtracks of the 1960s and 1970s Spaghetti western movies.
 They've released four albums, two on the German heavy metal record label AFM.
 They've also had guest appearances by many notable heavy metal musicians including Michael Weikath, Tobias Sammet, Joacim Cans, and Doro Pesch.
Tobias Sammet (21 November 1977) is a German musician, singer, songwriter and music producer best known for being the founder the Rock Opera Project Avantasia and singer and primary songwriter of the Heavy Metal band Edguy.
Holy Hell is a heavy metal album released in 2005 by Rob Rock.
 It is his third solo release and is known for being his heaviest and most aggressive album to date.
 It was produced by Roy Z who is also known for producing solo albums by Rob Halford and Bruce Dickinson.
 Roy Z is also credited for performing some of the guitar and bass parts on the album.
 Many highly acclaimed musicians are featured throughout, including guitarist Carl Johan Grimmark of Narnia fame, and drummer Bobby Jarzombek who has played in bands such as Iced Earth and Spastic Ink.
 Tobias Sammet of Edguy and Avantasia also makes a guest appearance, singing a duet with Rob on the closing track, "Move On".
Sly was a Japanese heavy metal band formed in 1994 by former members of popular groups of the Japanese metal scene.
 The line-up included singer Minoru Niihara and drummer Munetaka Higuchi (Loudness), guitarist Shinichiro Ishihara (Earthshaker) and bassist Koichi Terasawa (Blizzard).
 Sly disbanded in 1998, with Niihara and Higuchi re-joining Loudness in 2000 and Ishihara taking part in the reformation of his former group Earthshaker in 1999.
Canadian heavy metal music has a long history.
 Going back to the late 1960s, Canada has produced metal bands that have and continue to influence metal bands to this day.
 In 1964, Toronto-based band The Sparrows was formed.
 This band later changed their name to Steppenwolf and featured Canadians John Kay, Goldy McJohn and Jerry Edmonton.
 Steppenwolf's 1968 single "Born to be Wild" was the first use of the words 'heavy metal' in a song's lyric.
 In 1970, Woodstock, Ontario based Warpig released their metal music debut, which, although never reaching mainstream success like fellow heavy metal bands Black Sabbath and Blue Cheer, has become a cult favourite within the Doom metal scene.
Minoru Niihara (二井原 実 , Niihara Minoru ) (born March 12, 1960 in Osaka, Japan) is the original and current lead singer of the Japanese heavy metal band, Loudness.
Tobias "Eggi" Exxel (born 27 February 1973) is the current bass player for the power metal band Edguy.
 Tobias was hired by Edguy in 1998 when vocalist Tobias Sammet, who had played bass since the band's formation in 1992, decided the band should have someone who could focus on playing the instrument full-time.
On the Prowl is the ninth studio album released by the Japanese heavy metal band Loudness.
 It is also their second and last album with American vocalist Mike Vescera, before his leaving to join Yngwie Malmsteen's band for the album "The Seventh Sign" (1994).
 "On the Prowl" is mainly a compilation of self-covers of songs from early Loudness' albums, containing only three new songs written by the band (♠).
 However, Mike Vescera translated and adapted the lyrics of the old songs written by former vocalist Minoru Niihara, to be sung in English.