From Halopedia, the Halo wiki

This article is about the Halo 4 achievement. For the Halo 4 level or the Forerunner machine, respectively, see Composer (level) and Composer.
10 Gamerscore icon taken from Originally a single block colour (with the two circles both being white and the 'G' a transparent cutout), but modified by myself to display nicely on dark *and* light themes, and to be reminiscent of the pre-Xbox One gamerscore icon.

Composer is an achievement in Halo 4 and Halo: The Master Chief Collection. It is awarded to players for completing the seventh Campaign level, Composer, on any difficulty. The achievement is worth 10 Gamerscore. It is represented by a shield with a "7" inside it in Halo 4[1] and is represented by an image of the asteroid belt surrounding Ivanoff Station, as seen in the mission, in the Xbox art.