Players with the permission "visitor" are by default allowed to alter note block's pitches. This was first discovered by me while a friend of mine was making a note block song with the default permission being "visitor". Visitor permissions are not allowed to use doors and switches but are allowed to alter note blocks.
Steps to repeat
1. Have person with normal member permissions place a note block in their world that has default player permission set to "visitor"
2. Join that world and find note block
3. Right click on note block.