The part of the school week that is neither sums nor spelling. Two of these games are about colour and two are about sound, and all four can be checked by a child against something real.
Hearing pitch is a skill, and it is trainable
Telling a high note from a low one sounds obvious to an adult and is not obvious to a six-year-old. The pairs here are a full octave apart, which is wide enough to hear on an iPad speaker, and the order changes every time so the answer cannot be guessed.
Sound needs one tap first
A browser will not play anything until the screen has been touched once. The first tap of the round does that, so the notes work from the first question onwards.