When varying the sound quality of speech to maintain engagement, what aspect is being adjusted?

The aspect of speech quality being adjusted to maintain engagement in this context is pitch. Varying pitch involves changing the frequency of the sound, which can affect how the message is received by the audience. A speaker who utilizes variations in pitch can convey different emotions, emphasize important points, and keep the listener's attention focused. If a speaker maintains a monotone pitch, it can lead to a loss of interest among listeners. Thus, playful alterations in pitch help create a more dynamic and engaging speaking style that enhances communication effectiveness.