The open strings of bowed instruments sound brighter than the other notes, so that they give the keys in which they are used a great deal, especially those in which they are the key notes, a bright- er character. The natural tones of wind instruments sound brighter than those made by stops, etc. One's feeling for keys is undoubtedly affected by associations of various kinds. If a composer has written a powerful piece in d-minor, later musicians come unconsciously to associate that key with power.