Signal is the fourth extended play (EP) by South Korean girl group Twice. The EP was released digitally and physically on May 15, 2017 by JYP Entertainment and distributed by Genie Music.

It includes the lead single of the same name produced by Park Jin-young, a song that features a programmed Roland TR-808-style kick and hi-hat. Several producers and songwriters participated, including Twice's members Jihyo and Chaeyoung who wrote the lyrics for the fifth track "Eye Eye Eyes", while the third track "Only You" has lyrics written by former Wonder Girls' member Ha:tfelt.

On March 31, 2017, it was reported that Twice would be releasing their first full-length album before heading to Japan. However, JYP Entertainment quickly denied the news and stated that nothing was confirmed yet.

On April 18, the agency confirmed Twice's May comeback with no exact date of release. Nine days later, it was reported that the group finished filming the music video for the title track, which was produced by Park Jin-young.

On May 1, Twice shared an image teaser through their official SNS channels featuring the nine members wearing school uniform-styled outfits and confirmed the release of their fourth extended play titled Signal on the 15th. They also released the schedule of promotion for the album, including the 2-day encore concert of Twice 1st Tour: Twiceland The Opening on June 17–18 which was held in Jamsil Indoor Stadium. The next day, it was revealed that the EP has three versions with nine random CD covers.

Individual image teasers of the members, posed with both hands on their heads using letter Y of the American manual alphabet that look like two antennas, were released over the next few days. It was then followed by a series of video teasers featuring the nine members, an intro video with an enigmatic visual palette like a fantasy film that shows scenes of an alien with big eyes stroking a rabbit in the woods, and a spoiler video of the title track's instrumental.

The first music video teaser of "Signal" was released on May 13. The album, along with the music video for the lead single, was officially released on the 15th at 18:00 KST. It was also released as a digital download on various music sites.

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Wikipedia