Which companies are growing fastest in the Chicago area? Here are 50 on a roll: In our annual feature, which we’ve published since 2007, we identify the companies whose revenues are rapidly outgunning the rest. We start by profiling the top 10 firms to get an idea of what it took to make them grow; the other 40 are presented in list form. This list was produced with accounting firm Plante Moran. Click here to see how it was made. To apply to be on the 2020 list, click here. What it does: Online marketplace for music gear | 2018 revenue: $36.1 million | 5-year growth: 29,510.9% | Employees: 164 local, 180 total | Profitable: No | Location: Lakeview Entrepreneurs find inspiration in “pain points”—irritations with things the way they are, that could be better. David Kalt, who had been drawn to rock as a teenager, continually was irritated buying and selling musical gear on eBay and Craigslist. “The process, discovery and educational experience was limited,” he says. Buyers paid full price while sellers had to accept steep discounts. That frustration led Kalt to launch Reverb, a specialized site geared to musicians and collectors with detailed product descrip...