The antonyms for the phrase "high pitches" would be "low pitches" or "deep pitches." Low pitches refer to sounds that are generated through low-frequency vibrations and are characterized by a lower tone or pitch. They can be found in a range of music genres, including jazz, blues, and classical. Deep pitches, on the other hand, refer to the lowest pitches, which are often associated with bass instruments like tuba, bass guitar, or double bass. They create a powerful and resonant sound that can be felt as well as heard. Both low and deep pitches offer a counterbalance to the bright and vibrant sound of high pitches, creating a rich and harmonious soundscape.