You could go up into a building by taking the stairs or taking a ramp. The intermediate heights between bottom and top are quantized on the stairs, but continuous along the ramp.
Notes on a piano are fixed when the piano is tuned - you can only play the notes that the keys can hit. Notes on a guitar can be "bent" by stretching the string with your finger and changing the frequency.
Use an analogy to explain the difference between a continuous change and a quantized change
Continuous: trombone Quantized: piano or Continuous: Dial type clock Quantized: Digital clock In fact anything digital is quantized. The opposite is analog which is continuous.