Literal translation
he no longer sang as high
Meaning
he's toned down his boasting
Explanation
The image comes from singing, where reaching a high register demands confidence and vocal power: singing loud and high thus symbolizes someone's arrogance or displayed pretensions, while giving that up, lowering the tone, reflects a retreat of that same confidence, usually after a setback, a failure, or a rebuke that has brought those pretensions down to a more modest level. Saying that someone no longer sings as high means, therefore, that they have been forced to scale back their demands, arrogance, or ambitions, often after being put back in their place by events or by someone else. The expression matches the French idea of climbing down a notch or singing to a different tune, both resting on the same musical metaphor of vocal register applied to social confidence. The verb canta (to sing) and the adverb aut (high) alone build this simple, effective image. The register is familiar, often used with undisguised satisfaction by whoever is reporting the other person's misfortune.