Even wonder how to teach young toddler to differentiate loud vs soft sounds? Mummy really think hard about this but bear in mind that young ones are interested in actions and sounds... in other words it must be interesting to them.
So, take lion as an example, Mummy told En En lion papa is very fierce (just like her daddy) and roars the loudest. Therefore, mummy leads En En hands to press on the left side of the piano which sounds the loudest... just let her presses to get the most loudest sounds produced from the piano. Then at the middle is the lion mummy (to make sure she can differentiate) and lion baby's sound will be the soft one, at the right most of the piano. When mummy was leading En En to press on the keyboards, not forgetting to imitate the sound of lion's roaring in Loud,Medium and Soft. En En was very happy to notify the differences and is able to tell "lion papa" is on the left side and "lion baby" on the right side. Sounds cool, huh?
Right now, she will point to the piano and said "I-yen papa" and wants to press on the keyboard. She got it right BUT lately she introduced in "I-yen Ah Mah", "I-yen Ah Kong"! *slap forehead*