Hi Metalion,
I'm not sure how much this keyboards cost today, so please state your initial price. Keep in mind that the exchange rate of Euro versus Real is about 1 x 2,60. This means it will almost triple any Euro price you set. It will not make sense to spend almost a hundred R$ (quite a lot of money here) just to ensure the keyboards work with the MSX-Audios.
After the tests I'll not have much use for the keyboards except demonstrations on MSX fairs. I only know how to code, I have absolutely no musical skills.
If your keyboard is one-of-a-kind or a valuable item for you, its better not to sell it. I'm looking for keyboards in the following situations:
1) Someone who has two or more of them, so one will not be missed
2) Have one, but do not have any utility for it and is almost throwing it away to save space
3) Got married and his wife is just expecting an opportunity to throw it away

4) Just want to incentive the MSX development