Dr Jonathan Kemp of Kemp Strings, not content with inventing strings that facilitate new possibilities for the existing guitar and bass designs has recently invented a new way of making music with hot chocolate:
The hot chocolate effect, first explained in print by Frank Crawford in 1980, means different pitches can be heard on tapping a mug of hot cholcolate with a spoon because bubbles form and these vary the compressibility and therefore the speed of sound within the liquid. Stirring the mix redistributes the bubbles, slowing the speed of sound and lowering the pitch heard. Over time, the pitch will increase again as the bubbles rise to the surface. Dr Kemp has created a video of this process, shared by the Unviersity of St Andrews during Science Discovery Day 2022, and shows (for the first time as far as we are aware) how varying the timing and strength of stirring along with varying the timing of tapping with the spoon can produce a melody.