algorithmic ring tones

The GTK2 rendering engine Cairo has the option to use algorithmic rendering for the pictures that are the backgrounds for buttons. The idea is that you rapidly get bored of the same background on all the buttons in an interface, thus leading to a paucity of button decoration.

With algorithmic rendering, each background is generated on the fly, thus creating different backgrounds for each button.

In a similar vein, I have noticed how tired I get of mobile phone ring tones. There are very few rings that I mind hearing over and over again. But what if something similar could be applied here?

The problem is that we won't notice our phones ringing unless we notice the pattern in the ring. But I wonder what kinds of patterns are needed for recognition.

Could the pitch and ring tone be varied every time the pohone rings? How far can we go?

I even wonder if a ring tone could just be a silence mask imposed on an arbitrary sound segment.

Would we recognize a pattern of pauses in arbitrary music?

I'm sure somebody has already researched this...