[{"_id":{"$numberLong":"1234567890"},"playlists":[{"name":"ff","author":{"$numberLong":"123456789"},"tracks":[{"name":"name1","uri":"uri1","duration":100},{"name":"name2","uri":"uri2","duration":120},/**...*/]}]}]

db.collection.update({"_id":1234567890,"playlists.tracks.name":"name2"},{"$pull":{"playlists.$.tracks":{"name":"name2"}}})