Yeah - pretty sure a quintuple bypass would require the surgeons to have unfettered access to the heart.
As for the murmur - your quintuple bypass gave new pathways to arteries that feed blood to your heart. A murmur occurs from blood flowing through a heart valve, either on it's way into your ventricles, or on it's way to your lungs and the rest of your body. Though the valves are in close proximity to the transplanted bypass veins, they shouldn't have much to do with the murmur. Did you doctor indicate that something should be done about the murmur? Many times the murmur doesn't need any kind of treatment.
Traditional heart surgery, also called "open heart surgery," is done by opening the chest wall to operate on the heart. Almost always, the chest is opened by cutting through a patient's breastbone. Once the heart is exposed, the patient is connected to a heart-lung bypass machine. The machine takes over the pumping action of the heart. This allows surgeons to operate on a still heart.
The most common type of open heart surgery for adults is coronary artery bypass grafting (CABG). During CABG, surgeons use healthy arteries or veins taken from another part of the body to bypass (that is, go around) blocked arteries. CABG relieves chest pain and reduces the risk of heart attack.
Are you saying you had bypass surgery, for 5 arteries? If so, I believe that is not open heart surgery, that is the heart does not have to be cut open as it does for a valve repay. If this is your case, I don't see any relationship/connection between bypass surgery and development of a heart murmur, which I believe is due either to one or move valves for to a breakthrough somehow between chambers. I also believe most cases of heart murmur and benign, and do not require any treatment or medications... I do not have a murmur so I am speaking form what I have read, not from experience.