Fellini's creative process for La Strada started with vague feelings, "a kind of tone", he said, "that lurked, which made me melancholy and gave me a diffused sense of guilt, like a shadow hanging over me. This feeling suggested two people who stay together, although it will be fatal, and they don't know why". These feelings evolved into certain images: snow silently falling on the ocean, various compositions of clouds, and a singing nightingale. At that point, Fellini started to draw and sketch these images, a habitual tendency that he claimed he had learned early in his career when he had worked in various provincial music halls and had to sketch out the various characters and sets. Finally, he reported that the idea first "became real" to him when he drew a circle on a piece of paper to depict Gelsomina's head, and he decided to base the character on the actual character of Giulietta Masina, his wife of five years at the time: "I utilized the real Giulietta, but as I saw her. I was influenced by her childhood photographs, so elements of Gelsomina reflect a ten-year-old Giulietta."
The idea for the character Zampanò came from Fellini's youth in the coastal town of Rimini. A pig castrator lived there who was known as a womanizer: according to Fellini, "This man took all the girls in town to bed with him; once he left a poor idiot girl pregnant and everyone said the baby was the devil's child." In 1992, Fellini told Canadian director Damian Pettigrew that he had conceived the film at the same time as co-scenarist Tullio Pinelli in a kind of "orgiastic synchronicity":
I was directing I vitelloni, and Tullio had gone to see his family in Turin. At that time, there was no autostrada between Rome and the north and so you had to drive through the mountains. Along one of the tortuous winding roads, he saw a man pulling a carretta, a sort of cart covered in tarpaulin ... A tiny woman was pushing the cart from behind. When he returned to Rome, he told me what he'd seen and his desire to narrate their hard lives on the road. 'It would make the ideal scenario for your next film,' he said. It was the same story I'd imagined but with a crucial difference: mine focused on a little traveling circus with a slow-witted young woman named Gelsomina. So we merged my flea-bitten circus characters with his smoky campfire mountain vagabonds. We named Zampanò after the owners of two small circuses in Rome: Zamperla and Saltano.
Fellini wrote the script with collaborators Ennio Flaiano and Tullio Pinelli and brought it first to Luigi Rovere, Fellini's producer for The White Sheik (1952). When Rovere read the script for La Strada, he began to weep, raising Fellini's hopes, only to have them dashed when the producer announced that the screenplay was like great literature, but that "as a film this wouldn't make a lira. It's not cinema." By the time it was fully complete, Fellini's shooting script was nearly 600 pages long, with every shot and camera angle detailed and filled with notes reflecting intensive research. Producer Lorenzo Pegoraro was impressed enough to give Fellini a cash advance, but would not agree to Fellini's demand that Giulietta Masina play Gelsomina.
Fellini secured financing through the producers Dino De Laurentiis and Carlo Ponti, who wanted to cast Silvana Mangano (De Laurentiis' wife) as Gelsomina and Burt Lancaster as Zampanò, but Fellini refused these choices. Giulietta Masina had been the inspiration for the entire project, so Fellini was determined never to accept an alternative to her. For Zampanò, Fellini had hoped to cast a nonprofessional and, to that end, he tested a number of circus strongmen, to no avail. He also had trouble finding the right person for the role of Il Matto. His first choice was the actor Moraldo Rossi, who was a member of Fellini's social circle and had the right type of personality and athletic physique, but Rossi wanted to be the assistant director, not a performer. Alberto Sordi, the star of Fellini's earlier films The White Sheik and I Vitelloni, was eager to take the role, and was bitterly disappointed when Fellini rejected him after a tryout in costume.
Ultimately, Fellini drew his three leading players from people associated with the 1954 film Donne Proibite (Angels of Darkness), directed by Giuseppe Amato, in which Masina played the very different role of a madam. Anthony Quinn was also acting in the film, while Richard Basehart was often on the set visiting his wife, actress Valentina Cortese. When Masina introduced Quinn to her husband, the actor was disconcerted by Fellini's insistence that the director had found his Zampanò, later remembering: "I thought he was a little bit crazy, and I told him I wasn't interested in the picture, but he kept hounding me for days." Not long afterwards, Quinn spent the evening with Roberto Rossellini and Ingrid Bergman, and after dinner they watched Fellini's 1953 Italian comedy-drama I Vitelloni. According to Quinn: "I was thunderstruck by it. I told them the film was a masterpiece, and that the same director was the man who had been chasing me for weeks."
Fellini was particularly taken with Basehart, who reminded the director of Charlie Chaplin. Upon being introduced to Basehart by Cortese, Fellini invited the actor to lunch, at which he was offered the role of Il Matto. When asked why by the surprised Basehart, who had never before played the part of a clown, Fellini responded: "Because, if you did what you did in Fourteen Hours you can do anything." A great success in Italy, the 1951 Hollywood drama starred Basehart as a would-be suicide on a hotel balcony. Basehart, too, had been greatly impressed by I Vitelloni, and agreed to take the role for much less than his usual salary, in part because he was very attracted by Fellini's personality, saying: "It was his zest for living, and his humor."
The film was shot in Bagnoregio, Viterbo, Lazio, and Ovindoli, L'Aquila, Abruzzo. On Sundays, Fellini and Basehart would drive around the countryside, scouting locations and looking for just the right place to eat, sometimes trying as many as six restaurants and venturing as far away as Rimini before Fellini could find the desired ambience and menu.
Production started in October, 1953, but had to be halted within weeks when Masina dislocated her ankle during the convent scene with Quinn. With shooting suspended, De Laurentiis saw an opportunity to replace Masina, whom he had never wanted for the part and who had not yet been signed to a contract. This changed as soon as executives at Paramount viewed the rushes of the scene and lauded Masina's performance, resulting in De Laurentiis announcing that he had her on an exclusive and ordering her to sign a hastily prepared contract, at approximately a third of Quinn's salary.
The delay caused the entire production schedule to be revised, and cinematographer Carlo Carlini, who had a prior commitment, had to be replaced by Otello Martelli, a long-time favorite of Fellini's. When filming resumed in February, 1954, it was winter. The temperature had dropped to -5 °C, often resulting in no heat or hot water, necessitating more delays and forcing the cast and crew to sleep fully dressed and wear hats to keep warm.
The new schedule resulted in a conflict for Anthony Quinn, who was signed to play the title role in Attila, a 1954 epic, also produced by De Laurentiis and directed by Pietro Francisci. At first, Quinn considered withdrawing from La Strada, but Fellini convinced him to work on both films simultaneously, shooting La Strada in the morning and Attila in the afternoon and evening. The plan often required the actor to get up at 3:30 a.m. in order to capture the "bleak early light" on which Fellini insisted, and then leave at 10:30 to drive to Rome in his Zampanò outfit in order to be on the set in time to be transformed into Attila the Hun for afternoon shooting. Quinn recalled: "This schedule accounted for the haggard look I had in both films, a look that was perfect for Zampanò but scarcely OK for Attila the Hun."
Despite an extremely tight budget, production supervisor Luigi Giacosi was able to rent a small circus run by a man named Savitri, a strongman and fire-eater who coached Quinn on circus jargon and the technical aspects of chain-breaking. Giacosi also secured the services of the Zamperla Circus, which supplied a number of stuntmen who could play themselves, including Basehart's double, a high-wire artist who refused to perform when firemen arrived with a safety net.
Funding shortages required Giacosi to improvise in response to Fellini's demands. When filming continued into spring, Giacosi was able to re-create the wintry scenes by piling thirty bags of plaster onto all the bedsheets he could find in order to simulate a snowscape. When a crowd scene was required, Giacosi convinced the local priest to move up the April 8 celebration of the town's patron saint by a few days, thus securing the presence of some 4,000 unpaid extras. In order to guarantee that the crowd would not dissipate as the hours passed by, Fellini instructed assistant director Rossi to shout out, "Get the rooms ready for Totò and Sophia Loren", two of the most popular Italian entertainers of the period, and nobody left.
Fellini was a notorious perfectionist, and this could be trying for his cast. At an American Film Institute student seminar, Quinn spoke of Fellini's intransigence over selecting a box in which Zampanò carries his cigarette butts, scrutinizing over 500 boxes before finding just the right one: "As for me, any of the boxes would have been satisfactory to carry the butts in, but not Federico". Quinn also recalled being particularly proud of a certain scene in which his performance had earned applause from onlookers on the set, only to receive a phone call from Fellini late that night informing him that they would have to re-do the entire sequence because Quinn had been too good: "You see, you're supposed to be a bad, a terrible actor, but the people watching applauded you. They should have laughed at you. So in the morning we do it again." As for Masina, Fellini insisted that she re-create the thin-lipped smile he had seen in her childhood photographs. He cut her hair by putting a bowl on her head and shearing off anything that wasn't covered up, afterwards plastering what remained with soap to give it a "spiky, untidy look", then "flicked talc into her face to give it the pallor of a kabuki performer." He made her wear a WWI surplus cloak that was so frayed its collar cut into her neck. She complained: "You're so nice and sweet to the others in the cast. Why are you so hard on me?"
Under Fellini's agreement with his producers, any budget overruns would have had to come out of his own pocket, cutting into any profit potential there might be. When it became clear that there would not be enough funding to finish the picture, Fellini stated that Ponti and De Laurentiis took him to lunch and assured him that they would not hold him to it: "Let's pretend they were a joke. Buy us a coffee and we'll forget about them." According to Quinn, however, Fellini was able to obtain this indulgence only by agreeing to film some pickup shots for Attila that Francisci, the director of record, had neglected to complete.
While shooting the final scenes on the wharf of Fiumicino, Fellini suffered a severe bout of clinical depression, a condition that he and his associates tried to keep secret. He was able to complete the filming only upon receiving treatment by a prominent Freudian psychoanalyst.
As was the common practice at the time, shooting was done without sound; dialogue was added later along with music and sound effects. As a consequence, cast members generally spoke in their native language during filming: Quinn and Basehart in English, Masina and the others in Italian. Liliana Betti, Fellini's long-time assistant, has described the director's typical procedure regarding dialogue during filming, a technique he called the "number system" or "numerological diction": "Instead of lines, the actor has to count off numbers in their normal order. For instance, a line of fifteen words equals an enumeration of up to thirty. The actor merely counts til thirty: 1-2-3-4-5-6-7. etc." Biographer John Baxter has commented on the usefulness of such a system: "It helps pinpoint an instant in the speech where he [Fellini] wants a different reaction. 'Go back to "27",' he'll tell an actor, 'but this time, smile.'" Since he didn't need to worry about noise while shooting a scene, Fellini would keep up a running commentary during filming, a practice that scandalized more traditional filmmakers, like Elia Kazan: "He talked through each take, in fact yelled at the actors. 'No, there, stop, turn, look at her, look at her. See how sad she is, see her tears? Oh, the poor wretch! You want to comfort her? Don't turn away; go to her. Ah, she doesn't want you, does she? What? Go to her anyway!' ... That's how he's able ... to use performers from many countries. He does part of the acting for the actors."
Since Quinn and Basehart did not speak Italian, both were dubbed in the original release. Unhappy with the actor who initially dubbed Zampanò, Fellini remembered being impressed by the work done by Arnoldo Foà in dubbing the Toshiro Mifune character in the Italian version of Akira Kurosawa's Rashomon, and was able to secure Foà's services at the very last moment. Composer Michel Chion has observed that Fellini particularly exploited the tendency of Italian films of the post-war period to allow considerable freedom in the synching of voices to lip movements, especially in contrast to Hollywood's perceived "obsessive fixation" with the matching of voices to mouths: "In Fellinian extremes, when all those post-synched voices float around bodies, we reach a point where voices--even if we continue to attribute them to the bodies they're assigned--begin to acquire a sort of autonomy, in a baroque and decentered fashion." In the Italian version of La Strada, there are even instances when a character is heard to speak while the actor's mouth is shut tight.
Fellini scholar Thomas Van Order has pointed out that Fellini is equally free in the treatment of ambient sound in his films, preferring to cultivate what Chion has called, "a subjective sense of point of audition", in which what is heard on screen mirrors a particular character's perceptions, as opposed to the visible reality of the scene. As an example, ducks and chickens appear on the screen throughout Gelsomina's conversation with the nun, but, reflecting the girl's growing sense of enlightenment concerning her place in the world, the quacking and clucking of barnyard fowl dissolves into the chirping of songbirds.
The visual track of the 1956 English-language version of La Strada was identical to the original Italian version, but the audio track was completely re-edited under the supervision of Carol and Peter Riethof at Titra Sound Studios in New York, without any involvement by Fellini. Thomas Van Order has identified dozens of changes made in the English version, classifying the alterations into four categories: "1. lower volume of music relative to dialogue in the English version; 2. new musical selections and different editing of music in many scenes; 3. different ambient sound in some scenes, as well as changes in the editing of ambient sound; 4. elimination of some dialogue." In the English version, Quinn and Basehart dubbed their own roles, but Masina was dubbed by another actress, a decision that has been criticised by Van Order and others, since, by trying to match the childlike movements of the character, the sound editors provided a voice that is "childishly high, squeaky and insecure". It cost $25,000 to dub La Strada into English, but after the film started to receive its many accolades, it was re-released in the United States on the art-house circuit in its Italian version, using subtitles.
The entire score for La Strada was written by Nino Rota after principal photography was completed. The main theme is a wistful tune that appears first as a melody played by the Fool on a kit violin and later by Gelsomina on her trumpet. Its last cue in the penultimate scene is sung by the woman who tells Zampano the fate of Gelsomina after he abandoned her. This is one of three primary themes that are introduced during the titles at the beginning of La Strada and that recur regularly throughout the film. To these are added a fourth recurring theme that appears in the very first sequence, after Gelsomina meets Zampanò, and is often interrupted or silenced in his presence, occurring less and less frequently and at increasingly lower volumes as the film progresses. Claudia Gorbman has commented on the use of these themes, which she deems true leitmotifs, each of which is not simply an illustrative or redundant identifying tag, but "a true signifier that accumulates and communicates meaning not explicit in the images or dialogue".
In practice, Fellini shot his films while playing taped music because, as he explained in a 1972 interview, "it puts you in a strange dimension in which your fantasy stimulates you". For La Strada, Fellini used a variation by Arcangelo Corelli that he planned to use on the sound track. Rota, unhappy with that plan, wrote an original motif (with echoes of the "Larghetto" from Dvořák's Opus 22 Serenade for Strings in E major ) with rhythmic lines matched to Corelli's piece that synchronize with Gelsomina's movements with the trumpet and Il Matto's with the violin.