Grass Valley Maestro Master Control v.2.4.0 - Manual (Page 86)

MAESTRO User Manual 82
3rd Step: Audio Sets
Figure 38. Mono to Center Surround and Stereo Up Mix
Figure 39 shows the mono source mapped to the left front and right front
outputs equally.
Figure 39. Mono to Left and Right Front Surround and Stereo Up Mix
Figure 40 shows mapping to all three front speakers.