Just a heads up in Chromium version 68.0.3440.106 (Official Build) (64-bit) the midi's seem to be playing back at 10x or faster. In Firefox 61.0.1 (64-bit) at 2x or so. I'm on Ubuntu 18.04.1 LTS. Other generic web midi players play at the correct speed in either browser. Not sure if timidity has some timing issues that might be caused by the combo of OS and browser. Other than that, wonderful job and great idea!