Once you have mastered the basic peg system of Number Rhyme for your short term memory lists. 1 = bun, 2 = shoe, you can easily extend the number of items remembered by associating an element with the images.
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1-9 as normal
10-19 same imagery but everything is in Ice (i.e. one = bun, in a block of ice)
20-29 – same imagery where everything is blue (2-blue) (i.e. one = a blue bun)
30-31 – same imagery with everything as velvet. (i.e. one = a bun resting in velvet)
Etc