This week the SUMS talk is being given by graduate of USyd and recent postgraduate of Warwick, Dr Robert Tang. (Please note the change from the usual location.) Abstract: Suppose you wanted to write down a list of all possible triangles. Eventually, you’ll realise that this isn’t a very good idea. Instead of making a list, one could try using a space which naturally captures how the triangles organise themselves. I will describe how to do this, and discuss its connections with the space of 3-note musical chords. Expect paper models and lots of pictures.