Ask Mustang fans what’s their favorite part about owning the Ford pony car, and all of them will inevitably get around to saying the same thing; the sound. Though every Mustang has its own unique song, there’s nothing quite like the guttural growl of a Ford V8. The Blue Oval has sought to repackage that magic in a new way with the 2015 Mustang, and now we have a chance to hear what could be the top-of-the-line Shelby sing its song.

This latest spy video comes from California’s Mulholland Drive, where a camouflaged Mustang was recently caught testing, and it gives us our best listen yet at whatever engine is under the hood.

While one may think this is just another Mustang GT tester, you’ll note that this Mustang has several slight-but-important differences, like the quad-tip exhaust system. There also appears to be a large hood scoop or heat extractor towards the front of the hood, possibly funneling air to some sort of forced-induction system.

Of course there’s still the question of just which model Mustang this happens to be. It could be a Shelby GT350, keeping Ford’s alliance with Shelby alive for at least one more generation. Or Ford could revive one of the names it has used on past Mustang models, like Cobra, or Mach 1. We still think it’s most likely a Shelby model, but don’t let us discourage you from dreaming!