Guitar: A Sus4 in the Changes
Where A Sus4 sits once the key is named, and what this seat is responsible for while it sounds.
A Sus4 is A – D – E. Naming the notes is where a chord chart stops. A tune asks the next question instead, and that is the one this page answers.
A Sus4 has no third of its own, so it names no degree until something around it does — which is why it turns up as a suspension over a chord that already has a job rather than as a chord with one.
The guitar seat carries the comp — the changes stated in three and four notes behind whoever is playing the melody, which in practice means dropping the root and playing the notes nobody else is covering — the third and the seventh first, everything else only if it fits under the hand.
Every shape is drawn for EADGBE across 6 strings, the open ones first and the movable ones up the neck after them, and each one plays back so you can hear the voicing before you commit it to a chorus.