Not sure that the difference would make me sell a T4.
Maybe if I was a theater organist! I can't tell you how many calls a day I get to be one of those!
Baby steps, as usual from Yamaha... But at least, compared to Roland, ALL of the steps are in the forward direction!
If I had a T2, it would be a no-brainer, maybe even a T3 (if I'm well heeled), but T4 to T5? That's a tougher decision.
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An arranger is just a tool. What matters is what you build with it..!