 The songs of the album are noted for their changing dynamics - with " middle sections [ that ] turn into this mass orchestrated swarm and ridiculous time signatures " which include musical references to 1970s soft rock bands such as Wings , Eagles and Bread - summed by Hawkins by saying the band " wanted to make sure that everything ' built ' on this record , that each instrument started somewhere and went somewhere else in the course of a song " . The drummer attributed this to the acoustic tour leading the band to " shed some of the fear of incorporating mellower stuff with the heavy stuff " , and Grohl added that " we wanted the stops to be pin @-@ drop silent before exploding . If we had a beautiful melody , we 'd throw a fucking string quartet in there . So we did everything we could to really magnify all those elements and that was fun . Usually you have a few parameters you 're afraid to pass but , this time , there was no fear of going too far . " Mix engineer Rich Costey added that his work of " preserve what [ the band ] had done to a fairly large degree " with " balancing and rides to get the dynamics to happen " was difficult given the sonic variety of Echoes , which went from " [ the Foo Fighters ' ] endless walls of guitar overdubs , almost like a swarm of bees " to string quartets : " The challenge of this type of mix is to retain the power of the track , yet define a space for everything . " 
