Is music still allowed in cot rooms / sleep rooms in child care? If yes, are there any articles available?

Ensure that any music being played in sleep room does not impede your ability to hear babies who are sleeping or when doing sleep checks.
This is a regulatory issue & Red Nose does not have any specific recommendations for Safe Sleeping.

Some State regulators stress the importance of sleeping babies always being within sight & hearing range at all times.
Please check your Local Regulatory Authority &/or be guided by their information
What State are you from?

Red Nose, in consultation with NSW Dept Education has developed resources to assist with Sleep & Rest Policy & Risk Assessment.  https://rednose.org.au/page/early-childhood-educators