Incredibox:
"Incredibox is a music app that lets you create your own music with the help of a merry crew of beatboxers. Choose your musical style among 9 impressive atmospheres and start to lay down, record and share your mix."
Chrome Music Lab:
"Chrome Music Lab is a website that makes learning music more accessible through fun, hands-on experiments. You can play with these experiments across devices – phones, tablets, laptops – just by opening the site on a web browser."
Word Synth: "An experiment that lets you play with language and music."
Type Drummer: type any letter and make a beat!
Typeatone: Another program where you can type any letter and make a beat!
Sampler: Create a music loop and play with virtual instruments.