Only five prints of Double-Stop were produced when the film was released in 1968. Four of these were 35mm prints and the fifth was a 16mm print. One of the 35mm prints was used to create theatrical trailers, while the other three were edited from 91 minutes to 76 minutes and screened in theaters. One of these three surviving 35mm prints was used when Double-Stop was restored for its 2011 screening. The lone 16mm print (which was never edited from its original 91-minute length) was circulated to more than a dozen colleges and universities in 1968. This print was screened more than a dozen times in student centers which were not equipped with 35mm film equipment. This film has been partially restored (color corrected) and preserved on DVD, and it contains several "lost" scenes, including a different opening sequence, several scenes filmed on a tugboat, and additional footage of Katherine Westfall (Mimi Torchin) interacting with her art students..
Patti Bolog, who played the role of Susan, learned that she was pregnant the morning after being told she had won the part. Despite illness from the pregnancy, she kept her pregnancy secret from the filmmakers throughout the three-month-long shoot, fearing the role would be recast.
The film editor, Don Stern, had been on the sound editing team that worked on The "Sound of Music" (1965). Stern added his trademark thunderclap sound effect, also heard in the gazebo scene of "The Sound of Music", to the lovemaking scene that begins "Double-Stop". (When working on an industrial film for an asphalt company, Stern made sure to include a rainy scene so that he could incorporate the same sound effect.)
Photographer Flemming Olsen went to great lengths to set up many of the shots seen in Double-Stop. For one shot, Olsen shot the scene while perched near the top of a tree. Look for the scene in which Mike Westfall (Jeremiah Sullivan) and his son Pablo (Billy Kurtz) are driving in the convertible. All of the overhead scenes were shot by Olsen, who was supported by several crew members while in the tree.
As originally scripted, Pablo's pet was not a dog - it was an armadillo! About a week before shooting began, Billy Kurtz (who played Pablo) spent time playing with the armadillo so that the two would be acquainted with each other. Three days before filming, the armadillo died and was hastily replaced with an Afghan hound named Vladimir (Vlad, for short) who belonged to one of the Double-Stop crew members.