It is hard to remember long numbers. It is easier if you assign some rhythm to it, or a tune. No doubt this recruits other parts of the brain in the memorization task.

I propose that each numeral be assigned a tone. Thus any sequence of numbers would have a corresponding tune. The meter would
be arbitrary. Even if someone forgot the numbers, he or she could hum the tune and the numbers would naturally follow. This system could be used to memorize any string of numbers. Perhaps a website could take the numbers, interpret the tones, then assign known rhythmic structures (eg: girl from Ipanema, Jingle Bells, etc).

uhmmm.. interesting idea, but about as feasible as remembering your telephone number by the key tones. Probably easier to just memorize the number. Also.. let's all?

It would be just my luck if my number accidentally corresponded with Brotherhood of Man's "Save your kisses for me" or some similar guff. Neat idea though bung.

The problem with using telephone touch-tones to memorize numbers is that those are a mix of two frequencies (one for the row, one for the column), and some people (including myself) have trouble hearing the difference.

The problem with just using tones is that, unless you have perfect pitch, 12 and 23 may sound an awful lot alike.

So, maybe each number could be an interval - small numbers going up: 0 being c-c, 1 c-d, 2 c-e, and so forth, larger numbers going down: 9 c-b, 8 c-a, 7 c-g, 6 c-f, 5 c-e. Intervals add up: 123 is c-d-f-a. Of course, you might run out of your singing range over the course of a credit card number.

Alternatively, each sequence could start with an identical foundation tone that isn't part of the number.