I repeated the previous experiment but using a midi controller instead of the touch screen. So, I hooked up a CME XKEY 25 to each android device (with the help of a USB OTG adapter) and put the mic close to the controller to pick up the sound of my finger hitting a key, then loaded the resulting recording in audacity and measured the time between the key press and the sound.
That gives better latency; compared with previous results:
| Nexus 9 | Nexus 6 | |
|---|---|---|
| touch screen | 45ms | 50ms |
| midi controller | 20ms | 35ms |
That was again with "music synthesizer", one of the Android Apps that feels low latency. It would be interesting to measure the difference when using one of the apps that feels more laggy.
It'd also be interesting to compare to a hardware synthesizer, but the only one I have at home has fully weighted keys and probably doesn't sound till the key is somewhere in the middle of the stroke, so it's hard to know what exactly to measure.