Does anyone have experience playing in arabic scales? Yamaha keyboards have presets for these scales (which have many quartet tones as opposed to western half tone scales).

The question is, if I use one of the preset Yamaha Arabic scales, which key do I have to play in so that the tones sit in the right places?

Help is much appreciated.

try to lower the E and B a quarter tone, and play every white keys

Chony,
First, if you go to the function where there is scale tuning you will see a parameter called "base note". It defaults to "C" but you can change this to any note you want the interval that is either set by a preset quarter tone tuning or one you program yourself.
As an example if you choose "arabic 2" the major3rd (E) is going to be -50 cents and the 7th (B) will be -50cents. If you use the transpose function the arabic detuning will still be correct with the Major3rd and 7th always sounding detuned. If you do not want to use the transpose function and want to play in a specific key with the arabic scale correct than you can change the "base" key.