Interactive music websites suited to secondary age.
There's all sorts of fun to be had on interactive music websites which can turn your PC keyboard or mouse into a musical instrument. Some work on a phone/tablet, but some need a computer keyboard. These can be used as part of home-education, or for constructive fun and entertainment!
Perform - make music live within your browser
Incredibox Beatbox Looper - Animated beatboxers perform whichever samples you choose. Several different soundbanks to choose from, and you can mix by muting some tracks. Great fun!
Launchpad - a version of the iPad app that you can use in a browser. You can also plug in your hardware launchpad if you have one. Top-notch quality and with some practice you can perform like the pro's.
Sampulator - trigger samples with your computer keyboard to create your own performance. You can record your tracks using the built-in sequencer, and save them. Lots of fun, and a great introduction to music production!
Hip Hop sampler - perform and remix some of the samples used by Kanye West, 9th Wonder and J Dilla. Three banks of sounds to choose from. And you can try mixing it with drumbeats or other music created in other web apps.
Superlooper - record loops from drums, bass, chords and synths using your keyboard or mouse. Then layer and mix them.
Sequencers - a good introduction to music production and composition. Online sequencers let you do in a browser much of what you could do with DAW software (Digital Audio Workstation) such as Cubase or Logic.
BandLab for Education - a safe space for "walled garden" classrooms to explore all the fundamentals of music production - from composing and using virtual synths, to recording audio and mixing tracks. All free!
Soundation - A similar take to BandLab, but it has loads of loops. Very useful, but you can only save 10 tracks unless you pay a subscription. You have to be 13 or over to sign up, as there is a social element to Soundation.
Online Sequencer - A good introduction to using "piano roll" for sequencing, with a good range of sounds available.
Pulseboy - very retro. Use a tracker interface to sequence 8-bit sounds to make old-school game music.
Online Synths exploring the principles of how to create your own sounds:
Viktor - recreates an analogue synth.
(Requires Chrome browser). A virtual synth that lets you play using your PC keyboard, and record loops on the 4 track recorder. It also has a drum machine to play along with.
Also by Dreampipe is this virtual drum machine:
https://html5drummachine.com/virtual-drum-machine/