PBS Kids has many fun games. Some like Sesame Street's Monster Music allows you to be the composer and create your own music!
http://pbskids.org/games/music/

Composers for Kids is best suited for Pre-K to 2nd grade students.
http://www.starfall.com/n/level-b/music/load.htm?

This New York Philharmonic Kids website offers games about instruments and composers.
https://www.nyphilkids.org

Chrome Music Lab allows you to explore music and its connections to science, math, art, and more!
https://musiclab.chromeexperiments.com/

Incredibox allows you to create your own music using digital beatboxing.
https://www.incredibox.com/

Whack a Note is a great game for older students to practice the notes of the treble clef.
http://artsedge.kennedy-center.org/interactives/steprightup/whackanote/

Young Person's Guide to the Orchestra is an interactive game that teaches students about the instruments in the orchestra.
https://listeningadventures.carnegiehall.org

Here is a link to the Berlin Philharmonic Digital Concert Hall. Create an account by March 31 to receive 30 days of free access to all concerts in the digital concert hall.
https://www.digitalconcerthall.com/en/

This link is for concerts from the Detroit Symphony Orchestra.
https://livefromorchestrahall.vhx.tv/browse