Chrome Music Lab is a collection of 13 free online musical ‘toys’ that let kids (and adults) play with music and in the process, learn something about pitch, rhythm, and structure.
Each ‘toy’ (or ‘experiment’ or ‘app’ etc.) focuses on a different aspect of music and all differ in how technical they are. None are difficult to use. Young (3- or 4-years old) kids seem to enjoy Kandinsky and Oscillators, which make fun musical sounds based on the user’s mouse movements. While slightly older kids can get into constructing melodies, playing with modifications of their voices, or exploring visualization of tone and rhythm.
Overall, it’s fun and educational for kids, and a great alternative to videos or video games during ‘screen time’.
From their website: "Chrome Music Lab is a collection of experiments that let anyone, at any age, explore how music works. They’re collaborations between musicians and coders, all built with the freely available Web Audio API."
The site is not just free, but has no ads of any kind.