This is often a subject brought when we are discussing the most All-rounders/Ace idols.
Some people think we should focus only on skills that are known are "idol jobs" such as singing, dancing, rapping and overall performance/stage presence. While writing/composing/arranging isn't their "job" as idol, but separated skills they may or not have and/or execute. Others think any musical-related skill is valid to define an idol as an-rounder/ace.
What do you think?