[hasenj]

I'm thinking about a music application that lets you place tones in arbitrary locations on a continuous line (representing the tone space) and assign them keys on the keyboard.

[ThomPete]

Something close is

http://www.morphwiz.com/

and

http://misadigital.com/index.php?target=home&lang=en

They are both interesting because they are using touchscreen meaning that they are fretless.

[gtani]

Cool. I've started fretless bass, and reading about accommodations you make for playing with e.g. vocalists who run flat more often than sharp, or upper register of piano that are sharp.

[ThomPete]

Remember to check out Jaco Pastorious then!