an authoritative voice interspersed with a child’s...
Does the following text say that the soundtrack consists of three voices: 1. an authoritative voice, 2. a child’s voice, and 3. Hiller’s own voice?

Context:
Over the flame images, a soundtrack consisting of an authoritative voice interspersed with a child’s (Hiller’s son) recounting of a memory of seeing Rembrandt’s Belshazzar’s Feast, is combined with whispering, improvisational nonsense in Hiller’s own voice to invoke different mnemic registers that explore the interchange between image and word.

Question

an authoritative voice interspersed with a child’s...
Does the following text say that the soundtrack consists of three voices: 1. an authoritative voice, 2. a child’s voice, and 3. Hiller’s own voice?

Context:
Over the flame images, a soundtrack consisting of an authoritative voice interspersed with a child’s (Hiller’s son) recounting of a memory of seeing Rembrandt’s Belshazzar’s Feast, is combined with whispering, improvisational nonsense in Hiller’s own voice to invoke different mnemic registers that explore the interchange between image and word.

Answer

If you take out "interspersed with a child’s (Hiller’s son) recounting of a memory of seeing Rembrandt’s Belshazzar’s Feast, "

You get "an authoritative voice , is combined with whispering, improvisational nonsense in Hiller’s own voice "

So it does appear that there are three voices, but I am not clear what "an authoritative voice combined with whispering" means exactly. Are they two separate voices speaking over the top of each other or are they somehow combined into one. Who knows.

This kind of writing is difficult for native speakers so don't worry about it.