Actually, the tradition of the Orthodox Church is to have no musical instruments whatsoever in our temples or to use them during our services. There are unique exceptions, such as you obviously experienced, but these should never be considered the norm. I do know that some Greek or Antiochian parishes use organs, but only as a means of holding chords for the congregation to follow as they sing. Such instruments were – and are – never utilized to perform concert-type arrangements as one finds in many Roman Catholic or Protestant churches. 

It is true that various Psalms do mention praising the Lord with stringed instruments, pipes, drums, flutes, etc, although this never crossed over into the Early Church’s formal liturgical worship; nor might I add, were they part of the ancient Jewish liturgical worship either. There are indeed many instances of things mentioned in the Old Testament – such as the sacrificing of animals, for example – which have not been carried over into the New Testament Church, in which Christ becomes the sacrificial lamb and the human voice (acappella) becomes the musical instrument par excellence.