There a few options for accessing the Harmony Express, and Marmot is one of them.
When getting off at the Emerald Express or Big Red Express, take a left and follow signage to this run located skier's right of the Whistler Habitat Terrain Park.
This connector route will link you up with the base of the Harmony Express, and depending on the conditions up in that zone, you might have company on this run as you all scramble to get in line for this lift which accesses great terrain.
The only way out from the base is the very flat Sidewinder traverse, so only take this run if you are looking to ski the Harmony and Symphony areas.
Marmot as a run is narrow at points and can also get icy due to the amount of traffic.