What characterizes Hildegard of Bingen's "Alleluia"?

In Hildegard of Bingen's "Alleluia," the work is primarily characterized by the use of an a cappella choir along with a soloist. This vocal-only format is typical of Gregorian chant, which is the style that Hildegard exemplifies in her compositions. The absence of instrumental accompaniment allows the sacred text and the intricate melodic lines to take center stage, highlighting the ethereal and spiritual quality of her music. The soloist often performs soaring, expressive phrases that underline the emotional depth of the piece, while the choir provides harmonic support using simple, monophonic textures typical of medieval music.

This emphasis on vocal performance without instruments is crucial to understanding the context of the piece, as it reflects the liturgical traditions of the time and Hildegard's unique contribution to sacred music. The other choices involve combinations of instruments and varied performance styles that do not align with her traditional chant compositions.