下弦

下 = 一 + 卜 : Mnemonic symbol: from the up/down logic, and a little bit the shape of the character, a ladder.

Xi Shi (xi) is on a retreat in the ashram. Using a voodoo staff (卜), she divined that next (下) week she'll have to play the flute (一) sixteen hours per day. Because she hates playing the flute, she climbs over the ashram's bathroom (a4) wall using a ladder (下) to escape.

弦 = 弓 + 玄 : Marie Curie (xi) is getting trapped by black lava (玄) in the anthill's kitchen (an2) and all she has is a composite bow (弓). She plucks the string (弦) of her bow so that the chord (弦) resonates with the lava, causing it to stop its flow.