The OP asks about the “strongest voice”
STRENGTH: the quality or state of being physically strong.
Synonyms: power, brawn, brawniness, muscle, muscularity, burliness, sturdiness, robustness, toughness, hardiness, lustiness; More vigor, energy, force, might, forcefulness, mightiness.
Who talks about Bach and Mozart in those brawny terms? No one. Beethoven is the only one who comes close with his own explosive power and it is not necessarily related to his use of dissonance or complexity of counterpoint, but raw emotional power that’s personal. Slam dunk.
STRONG: able to withstand great force or pressure.
Synonyms: secure, well built, indestructible, well fortified, well defended, well protected, impregnable, impenetrable, inviolable, unassailable
Beethoven’s symphonies are architecturally strong and built like a brick house. He cared less what others thought of him and resisted the force of pressure of his deafness. Bach and Mozart were hardly weaklings when it came to power and strength but it was more controlled and refined as a creative force. They never raged over a lost penny. It was Beethoven.