Complex sentence: She gradually began to talk in a moderately lower and louder voice, and in addition to better articulating words she began to pronounce more individual sounds, but she frequently either outright deleted or substituted phonemes in her speech.
Split into simpler sentences: She gradually began to talk in a moderately lower and louder voice, and in addition to better articulating words she began to pronounce more individual sounds. Despite her progress, she frequently either outright deleted or substituted phonemes in her speech.