Low-pitched and Soft-spoken

Low-pitched adjective - Used of sounds and voices; low in pitch or frequency.

Soft-spoken and low-pitched are semantically related In some cases you can replace phrase "Soft-spoken" with "Low-pitched", this phrases are similar.

Soft-spoken adjective - Having a speaking manner that is not loud or harsh.

Low-pitched and soft-spoken are semantically related in quiet topic. Sometimes you can use "Low-pitched" instead an adjective phrase "Soft-spoken".