The Tangled Up Tour was the fourth concert tour by English-Irish girl group Girls Aloud. It supported their fourth studio album Tangled Up. Tour dates were announced in November 2007. Girls Aloud performed twenty-four shows at arenas across the United Kingdom and Ireland, making this tour their third to reach arenas. The tour commenced in Belfast on 3 May 2008 and concluded in Birmingham on 4 June. Girls Aloud also performed eleven open-air concerts over the summer.

"Sound of the Underground" is a song that was the debut single of British-Irish pop group Girls Aloud, and later featured on their debut album of the same title. The song was written by Miranda Cooper, Brian Higgins and Niara Scarlett, and produced by Higgins and his production team Xenomania. Following Girls Aloud's formation on the ITV1 reality television show Popstars: The Rivals, "Sound of the Underground" was released 16 days later, on 16 December 2002. Commercially, it was an immediate success; it became the year's Christmas number one in the UK, spending four consecutive weeks atop the chart. It also reached number one in Ireland and peaked within the top forty in Australia, Belgium, the Netherlands, Sweden and Switzerland.