Heh, for me that is a short answer - seven. I wish I could "collect" horns, but I usually sell one to get another. I still have a couple of decades to go, so maybe my collection will grow. This picture is from Leon Petre's studio in Belgium. This picture does not include other trumpets strewn across the room, quite a few in cases in another room and about ten natural trumpets in all keys decorating the entrance hall to his home. He has a dizzying collection in all keys and styles. Make sure to click on the picture so you can see the large version.