The influence of one piece (or style) of music on another is a perplexing issue. The continuum of musical references ranges from the subtlest detail (for example, a similarity in orchestration or a motivic resemblance) to whole-scale appropriation, and examples have been decried or defended as coincidence, plagiarism, incompetence, creative economy, tribute, poetic resonance and brilliant satire. ‘Borrowings’ have long attracted musicological interest; recent studies have turned to more subtle allusions and the meanings behind them. Christopher Reynolds's sophisticated analysis of motivic allusions in nineteenth-century art music explores a complex (and intentional) interrelationship between four parties:

The situation of musical allusions in the comic operas of Gilbert and Sullivan is somewhat more complicated. It is by no means clear that Sullivan's references were always intended to be recognised as such, nor indeed if he was always conscious of the allusions latent in his music. To be sure, there are clear examples of actual quotations which he expected to be recognised and appreciated: the fugue subject from Bach's G minor organ Fantasia (bwv 542) given to clarinet and bassoon as the Mikado sings ‘By Bach, interwoven with Spohr and Beethoven’ is only the most famous such case (‘Amore humane Mikado’, The Mikado, Act II).