Found a pitch stepping issue with the Linnstrument controller script

[tvdv]

While trying to figure out why pitch slides from my Linnstrument ended up sounding steppy when the recorded note data was played back, I found that using the “Roger Linn Design / LinnStrument” controller script that comes with Bitwig results in a “stepped” pitch curve, while using the “Generic” controller script resulted in a smooth curve for the same recording.

As a test I set up two tracks in Bitwig, one for each of these controller inputs. Then I recorded the same slide into both tracks:

Screen Shot 2018-05-08 at 20.41.34.png

Here’s a crop with the two tracks slightly offset in time so that the curves are easier to compare:

Screen Shot 2018-05-08 at 20.32.32.png

The blue track was recorded through the “Roger Linn Design / LinnStrument” controller script, the red track through the “Generic / Midi Keyboard” controller script.

As you can clearly see, the stepping is somehow introduced by the “Roger Linn Design / LinnStrument” controller script. Using the “Generic / Midi Keyboard” controller script, the recorded curve ends up being much smoother.

Comparing the controller script source code, the issue might be related to the “MPE mode” triggered by the “setUseExpressiveMidi” method on the note input.

I also recorded a video demonstration of this issue which can be found at https://vimeo.com/268771924

Here are step-by-step instructions in case you own a LinnStrument and are interested in testing with your own setup:

1. Connect the LinnStrument to the Mac using an USB cable. Make sure the LinnStrument is in “MPE Mode”.
2. Launch Bitwig.
3. Go to “Settings” and click “Controllers”.
4. Click “Detect available controllers”.
5. Confirm that “Roger Linn Design / LinnStrument” is detected and active.
6. Click “Add controller manually” and select “MIDI Keyboard” under “Generic”.
7. Confirm that “Generic / Midi Keyboard” is added and active. Select “LinnStrument MIDI” as its input.
8. Exit “Settings”.
9. Create a new Bitwig project with two instrument tracks.
10. Add the same instrument using a simple patch on both tracks, for example the “Pure Sine” patch from the Organ instrument.
11. Click “Show track input/output routing”.
12. Set the note input of the first track to “Roger Linn Design / Linnstrument”.
13. Set the note input of the second track to “Generic / Midi Keyboard”, choosing “All Channels”.
14. On the second track, enter the values “-24” and “24” under “Convert Pitch-bend”.
14. Arm both tracks for recording. The goal is to record the same incoming MIDI messages to both channels, each using a different controller script.
15. Record a one-octave pitch slide.
16. Compare the recorded pitch micro-expression data of the same slide in both tracks.
17. Notice that the slide recorded on the first track using the “Roger Linn Design / Linnstrument” controller script is steppy instead of smooth.
18. Notice that the slide recorded on the second track using the “Generic / Midi Keyboard” controller script is smooth and closely matches the slide gesture as it was performed.

For reference, my setup for this test consists of:

- Bitwig Studio 2.3.4 (build date 2018-05-03)
- macOS High Sierra 10.13.4 (17E202)
- Macbook Pro (15-inch, 2017) 2.9 GHz Intel Core i7
- LinnStrument running the latest firmware (version 2.1.0)

[Whywhy]

The same happens with pressure.
Generic script: no smoothing, perfect timing but no mpe.
Mpe script: to much smoothing when playing, difference between what you listening and recorded data.
Bitwig, please, fix it, it's really annoying.
Using another daw for mpe is funny but annoying.

[hydrogxn]

i wonder if the developers are even aware of this issue. maybe send s bug report?