Okay, a DJ created a mashup of Rick Astley and Nirvana (yes, you are about to be Rick-Rolled). Listen to/watch the video and tell me if Rick and Nirvana are using the same tonic, or two different tonics. Show your work.
I heard it as one tonic, with Rick creating some very extended harmonies and dissonant non-chord tones at points. Is this because I expect blues-influenced music to go beyond the triadic norm, or because my brain wants to find the simplest pattern to fit all the information? In other words, did I come to this conclusion top-down (schema driven) or bottom-up (sequential event expectancies)? Likely the two "strategies"* reinforced each other. I do know that if there were fewer common tones, or if the genre had led me to expect more melodic tonal closure, I would have heard two separate tonics, a la Milhaud.