"He seems determined to make a trumpet sound like a tin whistle"

With the words "He seems determined to make a trumpet sound like a tin whistle", Aneurin Bevan crafts a vivid metaphor to express criticism toward someone's actions or approach. The trumpet and the tin whistle are both musical instruments, but they differ greatly in their sound, prestige, and associations. A trumpet holds a strong, resonant, and commanding presence, often symbolizing grandeur, authority, and significance. The tin whistle, by contrast, produces a lighter, simpler, and less majestic tone, often considered a more humble or unrefined instrument.

By claiming someone is intent on making a trumpet echo the modest timbre of a tin whistle, Bevan suggests an intentional diminishment. There is an implication that something of great potential value, power, or dignity is being handled in a way that suppresses those qualities, reducing it to something ordinary, unimpressive, or even trivial. Instead of allowing the full power or resonance of the trumpet to be experienced, the person insists on restraining it, aiming for an outcome that falls short of what is possible or desirable.

The metaphor points toward a form of mismanagement or underutilization. It conjures the image of someone refusing to embrace the capabilities or purpose inherent in a tool, institution, or opportunity, preferring instead that it perform a lesser role. This could be interpreted as a criticism of someone who, perhaps out of timidity, lack of vision, or deliberate sabotage, refuses to let greatness flourish. The phrase also carries a tone of wastefulness, perhaps even contempt, as if the person is being both willful and stubborn in their intent to deny the true qualities of the trumpet.

Ultimately, Bevan uses the contrast between the grandeur of a trumpet and the simplicity of a tin whistle to highlight the folly of aiming low when given the means to achieve much more, reflecting frustration with small-mindedness or mediocrity when there is capacity for distinction and excellence.