What is a Spartan?
From Halopedia, the Halo wiki
What is a Spartan? is the first track in Halo Infinite Multiplayer: A New Generation Original Soundtrack, and plays during the Cinematic Intro for Season 01: Heroes of Reach of Halo Infinite multiplayer.
The track opens with the melody of Weight of Failure (from Halo 2: Original Soundtrack) on strings and choir, soon accompanied by bass and heavy drums. The strings continue, joined by an electric guitar, followed by synth. They pause, with the male choir singing a variation of the Halo Theme Gregorian chant. The percussion returns loudly, with strings growing more suspenseful, interjected by the choir's hopeful singing. The electric guitar and drums join in, playing a quick and upbeat melody. The music comes to a stop, with just the choir humming in ambiance. A solo piano enters, playing the fanfare of Finish the Fight (from Halo 3: Original Soundtrack), with drums joining for the two notes in the fanfare. They are joined by strings and the electric guitar, playing an upbeat melody, ending on a climax.
The name of the track is a direct quote from Spartan Laurette Agryna during the cinematic intro when addressing the Spartan recruits.