While most productions opt to use makeup to remove the "sheen" and facial hair stubble prior to shooting, Mystic Voices instead chose to take the chance of alienating viewers by purposefully "greasing up" the faces of the 17th century figures being represented on screen, and even insisted upon weighing down the hair to give it an unwashed, more historically accurate look. Going on the notion that many people of the period being portrayed (1637) might have been survivors of malnutrition, harsh elements and small pox, director Guy Perrotta chose to encourage hair and makeup teams led by Bernard de la Rivera to create an unromantic, less glamorous depiction of the real life people being portrayed by actors during the reenactments and dramatizations.
Many of the cast chosen for dramatic reenactments and dramatizations were descended from people who actually took part in the Pequot War of 1637 and other historical events portrayed.
During screenings at film festivals members of the audiences reported seeing strange faces whenever fire is portrayed on screen; additionally, unusual "mystical" voices have been claimed to have been heard on the soundtrack.
When the filmmakers first considered celebrity narrators it was suggested to work with Keir Dullea, a neighbor of producer Guy Perrotta and whose wife, Susie Fuller, was once Perotta's acting teacher. When the narration was recorded sometime later, Louis Edmonds was set to start when he was taken ill with throat cancer. Edmonds suggested that the producers work with his neighbor, Roy Scheider.
To try to bring the viewers back into the 1600s Guy Perrotta worked with the actors to avoid standard, "Received Pronunciation" (Queen's English) for the English portrayals. Among the "Mystic Voices" heard in the film are several accents and dialects used to depict various speech patterns in the 17th century, including English (East Anglia, London), colonial Dutch and Native American (Algonquian speaking tribes).