The musicians process the melodies and the lyrics while listening to the operatic solos in the different areas of the brain. The neural network of the brain is quite complex, and the different activities follow different neural pathways. In the listening of the operatic solos, the lyrics and the melodies of the song are processed in the different part of the brain, and hence, different neural networks function during this processing.
Hence, the blank can be filled with 'neural networks'.
