"Mach" is a song by South Korean girl group Rainbow. The song was released on 20 October 2010, and was later included on their second mini album So Girls. The song is also the group's second Japanese single. It was released on 7 December 2011 in 4 different versions: 3 limited editions (CD+DVD, CD + 28-pages photobook and CD Only + Bonus track) and a regular edition.
A teaser photo with the concept of the song was released in 18 October. The song was released to follow up the promotions of the song "A". This version does not have a music video.
The song was produced by Sweetune (Han Jae Ho and Kim Seung Soo) and written by Song Soo Yun, who also produced their previous single "A".
The song debuted at number 38 in the first week and climbed to the number 19 on the following week, which is currently the highest peak of the song. The song ranked at number 193 on Gaon's Yearly chart with 216,200,537 points and with 925,573 digital copies sold.
The Japanese version follows the same concept of the Korean version. A teaser of the music video was released on 15 November 2011, on Universal Music Japan's YouTube account. The full music video premiered on 21 November on the TV station Space Shower TV.
the lyricist of Japanese version : Natsumi Watanabe, Yu Shimoji and NICE73. The B-side is a Japanese version of the song "Not Your Girl", previously released in Korean, on their debut EP Gossip Girl.
The physical single debuted at the number 9 on Oricon's weekly chart with 15,506 copies sold in the first week.