Just pondering whether there is a system that converts line graphs into series of rising and falling tones, while a voice reads out the x axis markers.

If you have multiple series, you could have different sounds running in parallel - sin wave, square wave or perhaps musical instruments each denoting a different series.

That might actually be usable if there was an automated system for creating them on the fly.

There's also this kind of approach https://www.youtube.com/watch?v=I9lquok4Pdk