Dev Question: is portamento across multiple keys limited by hardware?

[Michael Farr]

Is there any hardware limitation to sliding from one key to another? Sliding up a key (away from you) to change pitch is nice but I want to slide across keys several notes, right and left.

Imagine playing a third and and sliding your fingers into a 4th or 5th somewhere up the keyboard.

I'm a software engineer so I'm mostly interested if there is a hardware or architectural limitation that would be difficult to get around.

I realize the software would have to track individual touchpoints as the player transitions from one sensor to the next up the keyboard. 

Mike

[Andrew McPherson]

Hi Mike,

In principle this can work and I even did some experiments along these lines very early in the project. You need to look for a touch near the upper edge of one white key and near the lower edge of the next, with a similar vertical position. From this, if neither key is pressed, you can infer that it must be the same finger touching both keys. You could probably stitch the keys together into one long ribbon strip this way.

The main reason I haven't done this is that ergonomically it is less useful than it first seems: once you have a key pressed down, the neighbouring keys are no longer at the same level, so it would be uncomfortable and awkward to slide along the keyboard horizontally. Alternatively, you could use a second finger to do the sliding, but that can get in the way of traditional keyboard technique.

The ROLI Seaboard uses this kind of technique for bending and sliding, but of course that works because it is not a traditional keyboard action but a continuous, compressible surface. So there are advantages each way.

But of course, if you want to try to put something together, I'm certainly interested to see the results! Here you can find the code: http://code.soundsoftware.ac.uk/projects/touchkeys

Best wishes,

Andrew

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[Michael Farr]

Hi Andrew,

Thank you so much for monitoring and answering here.  Do you generate vibrato by comparing signals from adjacent keys?  Looking at the PCB picture from section 2.2 in your "TouchKeys: Capacitive Multi-Touch Sensing on a PhysicalKeyboard" the diamond shaped sense pads in the wide part of the white keys appear to be joined together in rows.  Thus, moving left or right on a single key still activates the same row.  To detect vibrato, then, when only touching one key,  the computed position of the touch would already have to take into account the signal from more than one key. Is this correct?    

Thanks,