When reflecting on his time with Holmes at a classical music concert, Watson uses imagery and a metaphor, as seen in the following passage:
My friend was an enthusiastic musician, being himself not only a very capable performer but a composer of no ordinary merit. All the afternoon he sat in the stalls wrapped in the most perfect happiness, gently waving his long, thin fingers in time to the music, while his gently smiling face and his languid, dreamy eyes were as unlike those of Holmes, the sleuth-hound, Holmes the relentless, keen-witted, ready-handed criminal agent, as it was possible to conceive.
Watson uses imagery here in order to bring readers more closely into the scene, describing Holmes as “wrapped in the most perfect happiness” as he “wav[ed] his long, thin fingers in time to the music” and displayed a “gentle smile” and “languid, dreamy eyes.” From these descriptions, readers are able to hear the music of the concert, visualize Holmes’s dreamy and happy demeanor, and feel the happiness emanating from the man.
These descriptions, as Watson himself notes, are quite counter to the metaphorical “sleuth-hound” persona that Holmes takes on when he is solving a case. (Like Holmes, the sleuth-hound dog breed is known for its tracking abilities.) Here, Watson demonstrates that Holmes is not the single-minded rational investigator that much of London society considers him to be—he also loves music and has moments of peace and ease.