Chrome Music Lab https://musiclab.chromeexperiments.com/
https://listeningtowaves.com/sound-exploration
Great tools to share how music and sound is used in the real world. Students can ‘draw’ sound with a spectrogram, and look at waveforms with the oscilloscope.
Drumbit https://drumbit.app/
Splice Beatmaker https://splice.com/sounds/beatmaker
https://apps.musedlab.org/groovepizza/
Honestly an awesome drum sequencer with some visual flare.
http://www.musictechteacher.com/music_quizzes/music_quizzes.htm