> To listen, go to bostonglobe.com/soundtrack. How can you tell it’s Boston Marathon season? By the foot traffic along Commonwealth Avenue in Newton. In the weeks leading up to the race, especially on weekend mornings, its sidewalks and carriage lane fill with runners rehearsing for the big show. You can hear their huffing and panting, the impressive rhythm of their strides, and the slurp-slurp of their sneakers lifting off the asphalt. Some are lost in their ear buds; others inherit the sounds around them — spring bird song, the ebb and flow of traffic, the suburban peace. Not everyone out there pounding the pavement will run the 117th Boston Marathon, of course. But many surely will. And for those who do, the better they know the 26.2-mile course, the less intimidating it is, or so I’ve been told. That may be especially true for Heartbreak Hill, the legendary, punishing crest before the final descent into Boston. In other settings, familiarity may breed contempt. In this case, my sense is that familiarity is a good thing. Come Monday, those runners who have prepared most diligently may not be happy, exactly, to see Heartbreak Hill rising before them. But nor will they be surprised at her might.