Thank you everybody for your advice. I own an Edirol R09hr and I like it. I recently recorded ony one performance with the recorder about 60-70 cm from the piano, 1mt 30cm high, pointing towards the string; the result came not bad, but I would like to upgrade.
I used to record my solo piano or chamber music concert with a mic (sony ecm979, I posted elsewhere) which I'll know in a bunch of days if it will be possible to repair or not.
So I'm reading around to search for something.
Some points on which I need your advice in choosing two miniature instead of a strereo, and please correct me where I'm wrong:
1) I'm pointing my attention on a stereo mic ( rode nt4, usable with edirol) only for easy set up and portability purpouse; a stereo mic is always cardioids, so there's no choice.
2) in case of two mono mics the option of two miniature would be for me the only alternative to two "big" mics; I could clip them on one stand (i.e. a stand for sheet music or something like this, easy to bring and discrete). That's why I need to compare two minature vs.a stereo mic and I stepped into noise specs, sensitivity etc. !
I don't have any limitation in placement (not stealth at all), from stage lip to very close miking ( even inside the piano), so I think (but not sure) that omnis would do a good job. If I use them spaced they would probably provide an accettable stereo image, and the sound is more natural and less coloured. Suggest me please what would do better between cards and omnis.
3)I can't afford dpa4060 and similar, so the option would probably be something like Church CA14 (omnis or cards?), battery box or preamp (I don't know if Church sells overseas-I live in italy). In your experience, how the church gear (or something on the price range) would do for classical unamplified music compared to a stereo mic?
4) My questions are not in general terms, but related to the use with my edirol R09hr; so any consideration about noise level, output, powering has to be made in relation to this deck.
Thank you very much for your kind help. I guess I will help somebody in turn. If you have questions on pianos or piano literature please ask...........

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