noun, plural -tos, adjective Music.| 1. | the lowest female voice; contralto. |
| 2. | the highest male voice; countertenor. |
| 3. | a singer with such a voice. |
| 4. | a musical part for such a voice. |
| 5. | the second highest of the four parts of a mixed vocal chorus, or the voices or persons singing this part. |
| 6. | the second highest instrument in a family of musical instruments, as the viola in the violin family or the althorn in the cornet family. |
| 7. | of, pertaining to, or having the tonal range of the alto. |
| 8. | (of a musical instrument) second highest in a family of musical instruments: alto saxophone. |

| var. of alti-: altostratus. |
The lowest range of the female singing voice, also called contralto. (Compare mezzo soprano and soprano.)