"Theme of Tara" is the main theme of Metal Gear and one of the most remixed pieces in the Metal Gear series, next to the "Metal Gear Solid Main Theme." It was originally composed by Iku Mizutani. It plays almost constantly throughout Metal Gear, except during alert phases, boss battles or when in Outer Heaven's lower basement areas. Its name originated with Hideo Kojima, who interpreted the beat of the theme as "ta-rah."
It was later remixed by KCE Japan Sound Team for the VR Missions featured in Metal Gear Solid, and subsequently was remixed for Metal Gear Solid 2: Substance's VR Missions (the "MGS1 Snake" mode), as well as Metal Gear: Ghost Babel's VR Missions. For the Hideo Kojima Red Disc, it was remixed by Kanichiro Kubo. It was then featured on the Metal Gear 20th Anniversary Music Collection as part of the medley track "Metal Gear 20 Years History ~Past, Present, Future~" which was supervised by Norihiko Hibino and Takahide Ayuzawa. Finally, it was remixed for Super Smash Bros. Brawl by Takahiro Nishi and featured on the Shadow Moses stage, as well as Snake's introduction in the Subspace Emissary (with a distinctly James Bond-esque beat).
The original version of the theme is featured in Metal Gear Solid 4: Guns of the Patriots as a collectible track for the in-game iPod, and the Metal Gear 20 Years History version is available from the games start as part of the track "Metal Gear 20 Years History Part 1." The original version was also briefly and faintly heard in the game itself during Act 3 as an Easter egg, in one of the buildings in Midtown. The Integral Podcast mentions that the music being heard was intended to imply that one of the occupants was playing the original Metal Gear.
The theme can be found in Metal Gear Solid V: Ground Zeroes as part of the "Déjà Vu" cassette tape in the Déjà Vu mission. It can be listened to during gameplay or selected as the music that plays when the chopper arrives. The theme's equivalent in the Jamais Vu mission for the Xbox 360/Xbox One versions of the game is "Pleasure of Tension" from Snatcher.