At similar rpm, why can a flat-plane Ferrari V8 scream while a cross-plane V8 burbles?

Answer: Banks receive even pulses

Extra rpm alone lifts pitch — Not quite. Higher rpm raises pitch, but the question holds rpm roughly constant to isolate the rhythm. A cross-plane V8 and a flat-plane V8 can both fire eight cylinders, yet send very different pulse patterns into each exhaust bank. That bank-by-bank spacing changes the timbre before the muffler gets involved. So rpm is a volume knob for pitch, but not the whole instrument.

Banks receive even pulses ✓ — Right. A flat-plane crank lets the firing pattern alternate more evenly between the two banks, so exhaust pulses arrive in a cleaner, more regular sequence. That regularity favors a sharper scream instead of the uneven burble associated with many cross-plane V8s. Ferrari also treats the exhaust line as part of the instrument, changing geometry, silencers, and bypass valves. The twist is that rhythm, not raw loudness, makes much of the identity.

Open tips alone add treble — Not quite. Opening exhaust tips can make a car louder and less filtered, but they cannot by themselves create the flat-plane pulse pattern. The crank and firing order decide how pressure waves are spaced before the sound reaches the tailpipe. If the pulse train is uneven, open tips mostly reveal that unevenness. The best exhaust tuning starts with the engine's rhythm rather than covering it up.