Title irony
This novel is called "Banjo: A Story Without a Plot." However, this is ironic because the novel actually does have a plot, although it is somewhat scattered.
Banjo's personality
Banjo is known for his happy, joyful personality. However, as the text progresses he ironically seems very different, becoming disillusioned and pessimistic.
Drinking wine
After Banjo's transformation into a more pessimistic person, one of his friends comments that "even the wine he drank afforded him little pleasure." This is ironic, as drinking used to bring Banjo a lot of joy.
The joys of life
Although the seamen live a life of financial struggle and frequent discrimination, they ironically find the joys in life. Although they struggle and suffer a great deal, they also have a lot of freedom to live their lives how they want to.
The stolen banjo
Banjo is known by this nickname due to the instrument he owns. A lot of his joy in life comes from music, so when his banjo is stolen it seems like an ironic twist of fate, as the thieves have essentially stolen his identity.