by other bands combining the two genres including Windir, Månegarm and Thyrfing. Predating most folk metal groups, the Spanish band Mägo de Oz was formed as far back as 1989 with a self-titled debut album, released in 1994. With nine members in their lineup, including a violinist and flutist, the band has evolved over the years into a combination of power metal and Celtic flavored folk metal. They have experienced strong chart success in their native Spain as well as in South America and Mexico. Slough Feg from Pennsylvania, United States also had an early formation dating back to 1990. Their self-titled debut album was released in 1996 and the band has pursued a "unique style of combining traditional/power metal with folk metal." The Czech band Silent Stream of Godless Elegy had formed in 1995 as a doom metal band "laced with Pagan imagery and adventurous enough to include violins and cellos alongside the expected modern day arsenal." With the release of their second album Behind the Shadows in 1998, the band began to use "folklore influences" in their music. Explosion The folk metal genre has dramatically expanded with the turn of the new millennium. At the forefront of this explosion, with a "revolutionary clash of tradition and amplification that set them apart", is a group from Finland known as Finntroll. The band was formed in 1997 with a demo recorded the following year and a debut album Midnattens widunder released in 1999. They have since developed a reputation for being "obsessed with all things trollish." Their lyrics are sung exclusively in Swedish instead of the Finnish language "apparently because this language was better to evoke the trollish spirit", even though the real reason for this lies in the band's original vocalist belonging to the Swedish-speaking minority. The music of Finntroll features a "real innovation" in the marriage of black metal music with a style of Finnish polka called humppa. Specifically, the band took from humppa "the alternate picking bass lines accompanied with the drumbeat, and the use of accordion." This unlikely mix of polka and extreme metal has received a mixed reception from critics. Andy Hinds of AllMusic laments the polka influence as undermining "the intended threat of a death metal band" while his colleague Alex Henderson praises the band for their "solid, consistently likable effort," declaring that Finntroll has set themselves apart from their peers "because of their