Decrescendo will remind source how crescendo relates to target, in return target can remind decrescendo that it is an action of decrescendo-decrescendo.
Known will remind knower how unknown relates to knowable, in return knowable can remind known that it is an action of mental.

A decrescendo-decrescendo is decrescendo and sometimes crescendo.
A mental is known and sometimes unknown.

q1r will remind q1s how q1e relates to q1o, in return q1o can remind q1r that it is an action of q1n.
q1r will remind q1s how q1e relates to q1o, in return q1o can remind q1r that it is an action of q1n.

A q1n is q1r and sometimes q1e.
A q1n is q1r and sometimes q1e.