That's an incredibly rare feat for any artist, let alone a duo whose inspired musicianship and honest lyrics leave their street credibility untouched by such towering industry benchmarks. Perhaps just as telling, Macklemore and Ryan Lewis were "the most streamed" artists on Spotify in 2013. Although they spent the fall of 2013 packing arenas all over the U.S. in support of The Heist, in the downtime between gigs they turned their attention to the music that will form its follow-up, and Metric Halo is with them along the way.

Capturing and working out ideas on the road is often seen as a balancing act between quick-and-dirty methods that are fast, on the one hand, and higher-quality techniques that take more time and thought to set up, on the other. Lewis largely avoids that compromise with a Metric Halo ULN-2 interface. "The ULN-2 is a pretty unique interface," he said. "It has two good-quality pre-amps and yet it's small enough to fit into a carry-on. It also acts as a great interface for Pro Tools, or any other audio program that I use. Macklemore and I have used it countless times on the road."

After using the Metric Halo ULN-2 for a short while, Lewis was alerted to Metric Halo's collection of seven plug-ins, sold together as the Metric Halo Production Bundle. He has already used a number of the plug-ins to mix new music in the studio and on the road. Among them are Character – a plug-in that models the sonic signature of a wide range of classic and contemporary audio gear; HaloVerb – an authentic-sounding reverb, Precision DeEsser; and TransientControl – a unique dynamics processor.

"Character is great when I'm not exactly sure what I want to do with something that doesn't have the right texture," Lewis said. "It can pull out different pieces that weren't there before. I love HaloVerb and use it all the time. It has a good variety of feelings and a full range of spring and hall sounds that work well on vocals and instruments." Some of Lewis' uses are particular to rap and hip-hop: "Rap vocals have a lot of punch and can get very sibilant. The Precision DeEsser does a great job of cleaning that up. Finally, I didn't expect the fairly simple TransientControl plug-in to be as useful as it turned out to be. Now it's one of my favorite plug-ins because it can capture the accents in a recording. For instance, when I have a break beat and I really want the snare and kick to pop, but I'd like to lose everything else in the recording, I use TransientControl."