Which type of exercise typically aids in developing specialized vocal techniques within a choir?

Using sirens as an exercise in choir practice can be particularly effective for developing specialized vocal techniques. Sirens involve sliding between pitches, which helps singers explore their vocal range, improve their pitch control, and enhance their ability to navigate transitions between different registers, such as chest voice and head voice. This exercise encourages flexibility in vocal production and can help singers gain more comfort with rare tonal shifts and dynamic variations.

In contrast, choreographic routines primarily focus on the physical movement aspect of performance rather than directly targeting vocal technique. Group theory lessons can assist in understanding musical structure and harmony, but they do not provide the same practical engagement with the voice as sirens do. Audience interaction may enhance performance skills and stage presence, but it does not directly contribute to the development of specialized vocal techniques. Thus, among the options presented, sirens are the most effective tool for improving vocal abilities within a choir context.