The Tyros4 will not sound completely different.

My guess is that it is an internal upgrade, much like the S910 was over S900.

Yamaha has an established customer base that already are pleased with the Yamaha sound and operating system.

I believe the Tyros4 is intended for Tyros and Tyros2 owners, as well as PSR users that want to upgrade.

Now is a good time to buy a leftover Tyros3.

Ian
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Yamaha Tyros4, Yamaha MS-60S Powered Monitors(2), Yamaha CS-01, Yamaha TQ-5, Yamaha PSR-S775.