Signature is an instrumental Nu Disco/House track produced by Palme, a composer whose true identity remains one of maimai's quiet mysteries. The prevailing theory among players identifies Palme as an alias of Dirty Androids, a producer well known for contributing to Konami's BEMANI series, the track's warm synth beds and steady four-on-the-four kick pattern fit comfortably alongside that artist's signature sound. Palme also contributed the song "Blessed" to CHUNITHM AMAZON, further fueling the alias speculation. The song was contributed to maimai MiLK as an original track, debuting on January 23, 2018 under unusual unlock conditions: it initially appeared only within a Survival Course called "厳選オリジナル楽曲ランダムコース" (Selected Original Song Random Course). Players could later unlock it with 5 Cheese from February 20, 2018, and it became available by default starting with MiLK PLUS. The English title carries a double meaning, as a noun it refers to a personal mark or sign (署名), and as an adjective it describes something characteristic or specially made (特製な), fitting for a piece that serves as both a musical calling card and a curated arcade original. The in-game music video was created by レク (Reku), as confirmed through their personal portfolio. On the gameplay side, the MASTER chart (current level 13, constant 13.5) was designed by Techno Kitchen and emphasizes slide patterns riding atop the track's four-on-the-floor foundation. The EXPERT chart (level 12, constant 12.4) was designed by はっぴー (Happy). The MASTER difficulty was originally a level 12 at launch and was adjusted upward over subsequent version updates, reaching its current level 13 placement from でらっくす Splash onward.