Destiny 2 - Symphony of Death - How to get Bones

Festering Bone 00:18:9
Ritualistic Bone 00:57:20
Bone Collector's Marrow 01:49:06

Festering Bone
You can play any public event in ’’HELLMOUTH’’

Ritualistic Bone
You need to complete Lost Sector In ‘’SORROW’S HARBOR’’

Bone Collector's Marrow
Go and search for Bone collector in ‘’ANCHOR OF LIGHT’’