These passages require a tremendous amount of current. Although this burst of current is required for only a short time corresponding to the brief, but intense, music sections, the power supply must be capable of delivering this current. If it can't, then the music may not have appropriate bass for example. Some people have gone so far as to say that the power supply determines the musical characteristics of the amplifier. If that is the case, then the type of rectification can be very influential on the overall sound of the amp.
Rectifiers provide the DC voltage for the tubes and circuitry.
Up until the advent of solid state rectifiers, vacuum tube amps used tube rectifiers. The rectifier needs to provide high voltage and high current. A tube amp may typically need 450-500 volts on the plate of the output tubes. At the same time, the output tubes may conduct up to 75-100 mA of current. Tube rectifiers are robust in design, and can handle high voltages and current.