Refers to the mezzo-soprano voice range or a singer with that range. Used in musical contexts.
She sang a beautiful aria in the mezzo-soprano range.
ソプラノ is the higher soprano range, while 中高音部 is the slightly lower mezzo-soprano range.
アルト is the lower alto range, while 中高音部 sits between soprano and alto.
Compound of 中 (middle), 高 (high), 音 (sound), and 部 (section), literally 'middle-high sound section', referring to the mezzo-soprano vocal range.