What term describes singing without instrumental accompaniment?

The term that describes singing without instrumental accompaniment is "acapella." This style emphasizes the human voice and can showcase a range of vocal techniques and harmonies, as no instruments are present to provide additional melodic or harmonic support. Acapella performances can vary widely, including solo singing or a large group creating intricate vocal arrangements.

In contrast, "canon" and "round" refer specifically to types of musical compositions or arrangements where different voices sing the same melody at staggered intervals, but they do not inherently indicate whether instrumental accompaniment is present. "Dynamics" pertains to the volume of sound, indicating how loudly or softly music is played or sung, and is unrelated to the concept of accompaniment. Therefore, acapella is the clear term that encapsulates the idea of vocal performance free from instrumental support.