Marazza was born in Milan in 1912 and became famous in Voiturette racing. He only participated in 13 races and only one of those was outside Italy. He was Maserati's most promising youngster who had graduated to the works team within six months of starting racing. He was killed at Monza.
His first race was on 30th May 1937 in the 40-lap Circuito della Superba Voiturette race at Genua. Marazza bought on old Maserati 4CS two-seater from motorcycle racer Guiseppe Gilera. The car had originally belonged to Count "Johnny" Lurani who had mainly used it for hill climbing.
Marazza qualified the old Maserati on the front row of the grid between Vittorio Belmondo and "Nando" Barbieri. Marazza held third position during the early part of the race, but on lap 4 he passed Barbieri and started to close in on Belmondo. On lap 29 the pressure told and Belmondo made a mistake. He hit a straw bale and spun. Marazza took the lead and went on to win his very first race.
Two weeks later he was out again this time in Florence. The competition was far stiffer this time and the entry list included Dreyfus, Bira, Whitehead and Tongue. René Dreyfus won the race in the works Maserati while Marazza finished in ninth place, four laps behind.
Marazza bounced back the following week to show that his first race was not a flash in the pan. In Milan he qualified on the second row and held third position in the race behind the Maseratis of Siena and Rovere and in ahead of Bira in his ERA. Rovere retired with engine trouble and Marazza took over second place, which he held to the finish.
Race four was at San Remo. Marazza started in the second heat alongside Varzi and Villoresi but Marazza had to retire after a coming together with Ferdinando Righetti when the latter tried to pass him at the Station Square.
A month later at the Berne GP at the Bremgarten circuit Marazza made his only international appearance. He qualified for the final and finished 6th in a race that was run in heavy rain.
He was an early retirement at the Coppa Edda Ciano at Lucca but he had made quite an impression and received an invitation to drive a works Maserati at the Circuito di Campione d'Italia, the last race of the season. Marazza had to hand over the car to Trossi who was fighting for the Voiturette championship. And though Trossi later retired he still won the championship.
In 1938 Marazza's first start for Officine Alfieri Maserati was at the Targa Florio in May. For the first ten laps Marazza chased Villoresi for the lead before managing to pass. But despite putting in a number of quick laps, he couldn't shake off Villoresi. And when Villoresi tried to re-pass him on lap 13, he slid, crashing into Marazza. Marazza's car was badly damaged but fortunately Aldo only picked up minor injuries.
Back behind the wheel at the Coppa Principessa di Piemonte in Naples. Race day was extremely hot. Trossi gave up the lead retiring after 10 of the 60 laps after the pit stops Marazza, who had been among the top three for most of the race, found himself in the lead which he never relinquished, taking the flag for his second career victory.
At Varese Marazza passed Teagno and Villoresi to finish second behind Cortese, while at Pescara he started on the front row and though he retired while running second.
Aside from his Voiturette races, Marazza also competed in the Mille Miglia in a Lancia Aprilia with a special aerodynamic body designed by Pininfarina, finishing 26th.
Marazza's last race was a voiturette race held in the morning before the Italian Grand Prix. The race featured a fierce battle between E Villoresi and Severi and Maserati drivers L Villoresi, Marazza, Cortese and Pietsch. Sommer's Alfa Romeo 158 crossed the finishing line emitting clouds of smoke, probably from a broken piston. Marazza, following Sommer across the line, failed to see the flag, continuing at unabated speed not realising that the race was over. As he entered Lesmo, with his view possibly obscured by the smoke from the Alfetta. The Maserati slid wide and somersaulted into the trees. Marazza was thrown high into the air and impaled on one of the branches. He was terribly injured and though he was conscious at the hospital where the administered blood transfusions, he died later that evening.
He is buried at the family grave at Civenna, close to Emilio Villoresi. A bronze model of a Maserati on his grave was later stolen. Marazza was a year younger than Fangio, would have been a future ace, and would doubtless have been in the forefront in 1939 with the new 16-valve Maserati.