Complex sentence: Failing health due to a bout of typhoid in 1945 followed by tuberculosis restricted him to lower his pitch to "B" and "B Flat" though in his prime, he always sang in "C Sharp" and "C".
Split into simpler sentences: Failing health due to a bout of typhoid in 1945 followed by tuberculosis restricted him to lower his pitch to "B" and "B Flat". Although in his prime, he always sang in "C Sharp" and "C".