The PSRS910 has many of the Tyros3 voices but none of the Tyros4 voices.
The PSRS950 has many of the Tyros4 voices and all of the PSRS910 voices as well.
The PSRS750 has all of the PSRS910 voices and none of the Tyros4 voices.
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George Kaye
Kaye's Music Scene (Closed after 51 years)
West Hills, California
(Retired 2021)