Free Student Access
I use this site often in my curriculum and in class. It is for Pre-K through 6th Grade. It is a wonderful resource and is organized by grade level and has an online learning portion. On this site you can find songs to sing along with, you can write music, dance, perform body percussion and finger play, learn and practice guitar or ukulele, or play recorder. There are also games for students to play to help them learn about music.
Flat.io
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This is a free online music composition program that students can write their own music. I personally use it often and encourage students to go and explore and see what they can come up with. Here is a tutorial on how to start writing music with the program.
The Metropolitan Opera
Free access to full length operas from the MET with educational activities and materials included.
The MET is also offering free operas nightly here.
The Vienna State Opera