The track "Stairway to Heaven", never released as a single, was the most requested and most played song on American rock radio in the 1970s. The group followed up the album's release with tours of the UK, Australasia, North America, Japan, and the UK again from late 1971 through early 1973. Led Zeppelin's next album, "Houses of the Holy", was released in March 1973. It featured further experimentation by the band, who expanded their use of synthesisers and mellotron orchestration. The predominantly orange album cover, designed by the London-based design group Hipgnosis, depicts images of nude children climbing the Giant's Causeway in Northern Ireland. Although the children are not shown from the front, the cover was controversial at the time of the album's release. As with the band's fourth album, neither their name nor the album title was printed on the sleeve. "Houses of the Holy" topped charts worldwide, and the band's subsequent concert tour of North America in 1973 broke records for attendance, as they consistently filled large auditoriums and stadiums. At Tampa Stadium in Florida, they played to 56,800 fans, breaking the record set by the Beatles' 1965 Shea Stadium concert and grossing $309,000. Three sold-out shows at Madison Square Garden in New York City were filmed for a motion picture, but the theatrical release of this project ("The Song Remains the Same") was delayed until 1976. Before the final night's performance, $180,000 ($ today) of the band's money from gate receipts was stolen from a safe deposit box at the Drake Hotel. In 1974, Led Zeppelin took a break from touring and launched their own record label, Swan Song, named after an unreleased song. The record label's logo is based on a drawing called "Evening: Fall of Day" (1869) by William Rimmer. The drawing features a figure of a winged human-like being interpreted as either Apollo or Icarus. The logo can be found on Led Zeppelin memorabilia, especially T-shirts. In addition to using Swan Song as a vehicle to promote their own albums, the band expanded the label's roster, signing artists such as Bad Company, the Pretty Things and Maggie Bell. The label was successful while Led Zeppelin existed, but folded less than three years after they disbanded. In 1975, Led Zeppelin's double album "Physical Graffiti" was their first release on the Swan Song label. It consisted of fifteen songs, of which eight had been recorded at Headley Grange in 1974 and seven had been recorded earlier.