Pitch stays the same. AOA, therefore back pressure, increases as speed decreases.
We are discussing the first 90° of the turn, leading up to “There’s 90°” in the chant.
Here’s a description of the first half of a chandelle:
“The pilot enters a chandelle at a pre-determined airspeed in the normal cruising range for the aircraft. To begin the maneuver the pilot first rolls the aircraft in the desired direction with the controls (the ailerons), and quickly but smoothly establishes a medium-banked turn. In most small aircraft (cruising speeds of 100–175 KIAS) this bank will be about 30° to 40°. This will begin a turn of the aircraft in the direction of bank. Simultaneously, full power is applied
and a smooth pitch up is started with the controls (the elevators on the empennage). The angle of bank stays constant during the first 90° of the change of heading,
while the pitch angle increases steadily. At the 90° point in the change of heading, the aircraft has the maximum pitch angle (which should be close to the critical angle of attack at the level stall speed of the aircraft).”
Now, the pitch should, in fact, stay the same for the second 90° of turn, but that’s not what I was addressing, which was the “hold pitch” chant prior to the 90° point.