Deacon's style was one that was rarely seen in rock bands during the 1970s. Rather than just serving a background role and playing root notes, he used the bass as a lead and rhythm instrument. Some of his basslines are very intricate and difficult to play, such as "The Millionaire Waltz", "I'm Going Slightly Mad" and "You're My Best Friend", granting his technique an affinity with Motown's lead style basslines. Some of Queen's songs, such as "Dragon Attack", "Another One Bites the Dust", "Body Language", and "A Kind of Magic", feature the bass as the main instrument. When performing with Queen, Deacon delivered a highly technical style, with numerous runs, walking basslines and tight quick note changes. Deacon mainly used his fingers, though sometimes he did use a pick. Two of his trademarks are licking his fingers when playing and sticking two picks under the pick guard. He generally did not play with a floating thumb and occasionally played with his thumb itself. His basslines are notable on "Crazy Little Thing Called Love", "Liar", "Brighton Rock", "Under Pressure", "'39", "You're My Best Friend", "I Want to Break Free", and "One Year of Love", to name a few.
Another trademark of Deacon's playing are his bass runs. In a 1975 review of Sheer Heart Attack, the reviewer wrote: "Only at the end would a new initiate to Queen recognise John Deacon's unmistakable trademark: the bass runs under the fade are a fast and facile as any to be heard. The least well known musician in Queen is one of his rock generation's most able."
