George Gruhn, the 71-year-old Nashville dealer who has sold guitars to Eric Clapton, Neil Young, Paul McCartney and Taylor Swift was strrolling the aisles of Winter NAMM. What others might see as a boom — the seemingly endless line of manufacturers showcasing instruments — Gruhn sees as two trains on a collision course.

“There are more makers now than ever before in the history of the instrument, but the market is not growing,” Gruhn says in a voice that flutters between a groan and a grumble. “I’m not all doomsday, but this — this is not sustainable.