Maybe Jim's suggestion will work but I have yet to try it myself so I do not know if it will. It is worth a try and Polarized Sunglasses are cheaper today than they were a few years ago.
Also about LCD technology. The best technology for bright light conditions at a fairly reasonable price may be the "Transflective" type. It is suppose to be 'excellent' for use in bright light situations.
"Transflective LCDs are a mixture of the reflective and transmissive types-(those that do not reflect ambient light), with the rear polarizer having partial reflectivity. They are combined with a backlight for use in all types of lighting conditions. The backlight can be left off where there is sufficient outside lighting, conserving power. In darker environments, the backlight is turned on to provide a bright display. Transflective LCDs will not "wash out" when operated in direct sunlight."
To be "best" for bright light situations the 'Characters' or 'Type' must be a "Positive Image". In other words, a light background with a dark character referred to as "Type" or dot, hence the term dot matrix. PS: I think the Tyros display is a 640x480 dots, ie., pixels or 'resolution' display. To be best for bright light situations the background image should actually be light 'grey' segments (background) with dark characters, ie., type or dots.
The Transflective image in a 'low' light situation is solved by the use of a "backlight" which could be turned on to make the image viewable in low light.
This would definitely solve the problem with different lighting situations but getting Yamaha or other Manufacturers to implement it could be as hard as trying to pull teeth from a little child.
Also Gary's solution sounds very interesting too but here again were up against Corporate Monstrosities whose very nature is cutting corners WHEREVER possible to save on costs and enhance their bottom line, ie., their profit margins WHENEVER possible. To get them to look beyond that and focus more on their customers wants and wishes is almost like trying to part the Red Sea.
In other words it would take a miracle for it to happen imo. But miracles can and do happen.
So I will remain optimistic that they will eventually solve the "LCD display working effectively in every environment and lighting condition" problem someday.
Best regards,
Mike