Per the artist official homepage, http://www.a-ha.com, the band's name is spelled all lower case.
Discussion about capitalization of the title "Take On Me": http://forums.musicbrainz.org/viewtopic.php?id=771
A-ha (usually stylized as a-ha; Norwegian pronunciation: [ɑˈhɑː]) is a Norwegian band formed in Oslo in 1982. Founded by Morten Harket (vocals, guitars), Magne Furuholmen (keyboards, guitars) and Paul Waaktaar-Savoy (guitars), the band rose to fame during the mid-1980s after being discovered by musician and producer John Ratcliff, and continued its global success in the 1990s and 2000s.
A-ha achieved their biggest success with their debut album Hunting High and Low in 1985. That album peaked at number one in their native Norway, number 2 in the UK, and number 15 on the US Billboard album chart; yielded two international number-one singles: "Take On Me" and "The Sun Always Shines on TV"; and earned the band a Grammy Award nomination as Best New Artist. In the UK, Hunting High and Low continued its chart success into the following year, becoming one of the best-selling albums of 1986. In 1994, after their fifth studio album, Memorial Beach, failed to achieve the commercial success of their previous albums, the band went on a hiatus.
Following a performance at the Nobel Peace Prize Concert in 1998, the band returned to the studio and recorded their sixth album, 2000's Minor Earth Major Sky, which was another number-one hit in Norway and resulted in a new tour. A seventh studio album, Lifelines, was released in 2002, and an eighth album, Analogue, in 2005, was certified Silver in the UK – their most successful album there since 1990's East of the Sun, West of the Moon. Their ninth album, Foot of the Mountain, was first released on 19 June 2009 and returned the band to the UK top 5 for the first time since 1988, being certified Silver there and Platinum in Germany. The album peaked at number 2 in Norway (their first release not to reach number one in their home territory).
On 15 October 2009, the band announced they would split after a worldwide tour in 2010, the Ending on a High Note Tour. Thousands of fans from at least 40 different countries on six continents congregated to see A-ha for the last leg of the tour. On 4 December 2014, A-ha officially announced its participation at Rock In Rio 2015 which celebrated 30 years for both the band and the event. In 2015, it was announced that A-ha would re-unite for two years. Their tenth studio album, Cast in Steel, was released on 4 September 2015. A tour, named for the album, in support of the album happened in autumn 2015 and March–May 2016.
The band has released ten studio albums, several compilations and four live albums. In less than a year, during 2010, the band earned an estimated 500 million Norwegian Kroner from concert tickets, merchandise and the release of a greatest hits album, making them one of the 40–50 largest grossing bands in the world. The band were listed in the Guinness World Records book for having the biggest rock concert attendance; they drew an audience of 198,000 at Maracanã Stadium during Rock in Rio festival. Another record for the band is for singer Morten Harket, who was (and is still) listed in the Guinness World Records book in 2001 for the longest live note held; he held a note in "Summer Moved On" for 20.2 seconds. According to their label, Rhino, they have sold 55 million records.