OK, this one might need a little bit of commentary!
This is a corner of the choir gallery at St Aloysius, North Caulfield. At one time the organ console stood here. The box on the left of the photo is the switch for the long-disappeared blower.
The organist would have had his/her back to the left hand side of the photo, and so would have had a view down the church by looking to the left. This is much easier than the mirrors and periscopes you find elsewhere, and doesn't require mentally inverting the view in order to see things the correct way round.
This would work most of the time. However, sometimes you can't see what is happening, like those occasions when the thurifer gets a little over-enthusiastic and the incense cloud obscures the sanctuary. Hence the warning bell in the centre of the picture. There would have been a button down in the sacristy to allow the organist to receive a signal for the entry of the sanctuary party, or the arrival of a bride, or the nearing completion of a prayer said in the vox mystica. This would allow the organist to tail off so that the next thing could happen down the front.
