If you frequent calculators, whether for school, work, or even simple multiplication, as much as I do, maybe you'd like to add a little allegro to you algebra to relieve the monotony.

To do this, simple home calculators (like the four-function one on your desktop) could produce tones much like that
of your average cellphone when you punch the keys. I actually got quite bored at a meeting once, whipped out my cell, and found that if I traveled far enough into the number pi, that I could produce the first measure of 'happy birthday' within the thing.

However, such calculator may already exist off of the cell phone. BUT, what I was considering was something a bit more musical. So, for more advanced calculators (like those used in upper high school and college level classes), actual music would occur not just with every key, but with graphs and data and the like. For example, a sine graph would basically be the repetition of a scale (or somewhat like crazy phillip glass music), and statistical data (like the stuff you would create a scatter plot with) would plot the points and create a tone for the position. This type of ability could actually prove useful in finding outliers (lower or higher tones)... but certainly the most interesting music would come from graphing complex multi-dimensional graphs and complex high-degree equations.

---
Although, I could imagine the effect on my calculus class during a test. "Hmmm... Billy's calculator played a D-minor chord followed by a diminished G-flat... mine ended in a G-natural... DAMN!"
There would have to be a silent feature here.

Synesthesia- Hearing the digits? - The chances are that any numerical sequence is embedded in pi somewhere... I found my own (local-dial) phone number near 27 million'th decimal point.

Dub's sonata in Hexadecimal... Ah, that has a ring to it!