[skybrian]

This is task-specific. Consider having a conversation in a foreign language. You don't have time to use a dictionary, so you must have learned words to be able to use them. Similarly for other live performances like playing music.

When you're writing, you can often take your time. Too little knowledge, though, and it will require a lot of homework.

[kjkjadksj]

There might be words I don’t use or chords I don’t know. It doesn’t matter though because part of expertise is being able to consult a reference and go “of course”, implement it, and keep moving.