A further fragmentation of the material brings us to (d.). This rhythmic cell is then chopped into (d1.) and (d2.), which reinforces the sense of urgency. All this material is also subject to octave displacement and expansion of registers (0:59 onwards): From a low A3, the fragments are interspersed with notes in the upper octaves (A4, A5). The note A6 is presented as an interval of an octave (A5 and A6) with a leap in register (1:31).
The first chord is a D major chord (D, F♯, and A), which makes the I (tonic) chord. The second chord consists of the notes C♯, E, and A, which make up an A major chord — also known as the V chord in this context because it starts on the fifth note of the D major scale. The third chord is a G major chord (D, B, and G), which is the IV chord because it starts on the fouth note of the D major scale.