The highlight of Fantasias for Guitar and Banjo is usually considered to be its opener "Blend", a lengthy improvisational piece. According to Bull, the ideas behind the piece originated from his admiration of Folkways Records, which documented ethnic music from across the world. He also claimed to being particularly inspired from hearing Ravi Shankar and Ali Akbar Khan in New York City. "Blend" has been viewed as a "virtual travelogue of styles done in a then revolutionary modal tuning". The tuning is in the key of B.
Matthew Greenwald of AllMusic describes Fantasias for Guitar and Banjo as an "incredible debut" and lauds it for being well ahead of its time. Writing in Crawdaddy in December 1966, Sandy Pearlman recognized the album as a work that presaged pop music's move toward raga rock. Pearlman said that, with Fantasias, Bull "became a leading innovator in the assimilation of Indian influences into a Western musical context".
Author Kevin Fellezs views the album as a prime example of an "underacknowledged early fusion-world recording that remains musically compelling today".