Chapman Stick - working really well, with a couple of troublesome exceptions

Hey all…

I’ve just started doing some “serious” work with MG2 and have run into a couple of problems that there may be some way to overcome. It could be that my instrument isn’t well suited to MG2, but I have two of them, and I’m running into different issues with each.

My instrument is a Chapman Stick. I think that MG2 is an ideal solution for Stick players as hexaphonic pickups are a) expensive b) difficult to install and c) becoming increasingly rare. To be fair, I’m extremely impressed with how well MG2 works! Just amazing. But as to the problems, read on.

I have two instruments, let’s call them Mr. Brown and Mr. Blue just to keep them straight. They have slightly different tunings which may be the cause of the different behavior I’m getting from the two instruments. Mr. Brown is tuned in Baritone Melody. Mr. Blue is tuned in Matched Reciprocal. What this means is that the 5 “melody” strings (the output of which is being run through MG2) on Mr. Blue is tuned 3 semitones higher than Mr. Brown. The strings on both are tuned in ascending 4ths just like a guitar (without that major 3rd we’re used to seeing at the “B” string). Mr. Brown is thus tuned on the “open” strings to C#(2), F#, B, E, A. Mr. Blue is tuned on the “open” strings to E(2), A, D, G, C. Thus as you can see, not significantly different than standard or drop-D tuning on a guitar. Note that I put “open” in quotes like that because on a Stick (not sure if this is true on a Warr guitar) the open strings are never played. It’s a “touch” or “tapping” instrument, basically using hammer-ons to sound the note. The lowest possible note that is playable is a semi-tone above the stated “open” string tuning, as you can’t “tap” the string against the nut. Something else to be aware of (and that could be contributing to the problem) is that the strings are (when compared to guitars) longer, having a scale length of 34"

On Mr. Brown, everything is working superbly until I get to the 5th string. It seems that MG2 can’t track the fundamental of most notes on that string, anywhere along the fretboard. It often tracks as a semi-tone low, or, particularly on a held note, will “stutter” between the note and an octave low.

On Mr. Blue, everything is working really well, including everything on the 5th string. However, on that instrument, MG2 is interpreting the attack as progressively softer as I move to higher strings, until I get to the 1st (highest) string, where at first I thought it wasn’t working at all, then realized I could either crank the volume on the amp, or hit those frets really, REALLY hard, to sound the note.

On both cases, I adjusted the “open” string tuning in MG2 for each. I didn’t know what to do with the 6th string, so I spec’d it as what it would be if I was playing a 12-string instrument (6 bass, 6 melody) but beyond that I’m at a loss as to what tweak I might be able to do to get this working across all strings.

If it makes any difference, I’m running MG2 within AUM on an iPad Air 4th gen. Input to the iPad is through a Focusrite Scarlett 2i4 USB audio interface.

Thanks for any suggestions!

Hello Steve, welcome here :slightly_smiling_face:

Have you tried changing the settings in the Midi Velocity window? Especially the Tone knob which adjusts the dynamic balance between the lowest and highest notes.

Gain and Curve can also be useful depending on how you attack the notes.

Different midi instruments may require different settings (which will be saved in a patch)

Thanks, Herold. I cranked the curve value to max as well as the tone, and that has made Mr. Blue very happy. No problems that I can see with those settings.

Mr. Brown though is same-old same-old. The settings I used to resolve Mr. Blue’s problems seem to work fine with Mr. Brown, but do not improve the tracking for the lowest (5th) string. I also notice that it also has problems with specific notes on the 4th string as well, but not consistently. I’m wondering if this instrument may have a richer set of overtones that is confusing MG2’s fundamental detection algorithm.

The fact that it works so well with Mr. Blue suggests this might be the case. Mr. Blue is made of anodized aluminum, whereas Mr. Brown is rosewood. They do each have a distinctive timbre which suggests a slight variation in the overtones.

I’ll also add that (to follow up on your comment wrt my “attack”) that these instruments, because they are tapped against the frets, not plucked with fingers or pick, they have a very different, persussive, somewhat piano-like attack. That too could be causing some confusion on the part of MG2.

it is mostly the “undertones”, lower frequency resonance in body and neck that cause problems for midi converters. Mr. Brown is bound to be more resonant, and therefore the fundamental frequencies are hard to distinguish. It is so that the resolution of any FFT is measured in an array of bins, where each bin has a certain frequency. The bins are spaced by a fixed hz distance (linear spacing). This means that the low frequencies have less resolution, because the music notes are logarithmically spaced.
Further the time required for getting a good separated evaluation of closer bass frequencies is longer as for the higher freqs. this means that to keep the latency reasonably low in midi conversion, tradeoffs are required.
Resonances in the lower frequency area are therefore hard for pitch to midi converters.
The only thing that is (theoretically) possible is: locate the resonant low frequencies and notch them out. Note that filters also introduce their own problems, hence the “theoretical”

2 Likes

Thanks for the explanation, Paul. It’s really interesting that MG2 has trouble with the wood Stick but not the aluminum model. There is definitely a timbral difference between the two that my tin ear can detect, but as a luthier, my experience is that for electric instruments a more rigid structure (one that is less prone to absorption of some of the sound energy) is a plus, but may actually have a frequency distribution more amenable to MG2’s algorithm, as I would suspect that more of the higher frequencies will come through with the more rigid platform.

I haven’t tried MIDI Bass, but I assume the developer has found some solution to this. TBH, I really like the sound of the aluminum Stick, but most of my study has required the tuning of the rosewood model. I find that using instruments with different attacks, timbres etc. can be very inspirational when doing composition or improvisation, and the fact that I have MG2 working well with that model will give me more excuses to play it.

Hi Steve

Another Stickist here. I have a feeling Stick is better suited to MG2 than guitar.
My main Stick is rosewood tuned MR. The main issue I encountered was getting open strings triggering notes when releasing tapped notes. This is controlled by adding extra damping material at the lower frets
I wonder, is the pickup on Mr Brown a Stickup? Those have 2 polepieces on every string except string 5 which then has a different character to the others.
Also BM is quite low so will be heavier stiffer gauge than string 5 on Mr Blue. If the string is aging it will throw out of tune overtones which could upset the pitch recognition.
The only time I had pitch instability it turned out I just needed to tune up.
Also, check your setup is optimised so you aren’t tapping sharp at higher frets. The lowest frets are of course below the trigger range of MG2.
Can’t think what would cause the octave warble other than crosstalk from the bass strings, which you can dial out with the sensitivity control.

Hopefully with some brainstorming we can sort you out!
Al

Thanks, Al. I believe Mr. Brown is equipped with Stickups. The strings are at least a year old, but I’m sure the PO put new strings on it before he sold it to me (a year ago December) – it had been stored away for quite a while, which is why he was willing to part with it (he’s an extremely good Stick player!!).

Interesting take on the tuning. I’ve been tempted to re-string the MR Railboard to Baritone Melody as everything I’m learning (all Bach compositions) requires either that or a 12-string and as I mention above, I’d really like to have more opportunity to use the Railboard. But if that will possibly cause problems with the Railboard wrt MIDI, well…maybe I’ll hold off on that. As to the instrument being in tune, I use a Peterson strobe tuner app on my iPad which seems to be the most accurate tuner I’ve ever used. Great for setting intonation. Also, I lowered the action by a HUGE amount when I got it. I even had to order shorter bridge screws from Stick Enterprises as the PO seems to like a very high action which could definitely sharp the higher frets. I lowered the action as much as I dared, and it seems to be well intonated throughout the range.

I would like to get this working as one thing I noticed right off is that if I’m prone to any sloppiness in my playing, the MIDI triggering is going to show that up right away!! Thus it’s a really good way to practice (someone on the Stickist forum likened to running with weights on your ankles…) so I’d love to be able to practice repertoire using the MIDI output.

Peterson app is the best! I have an old iPhone wired into my rig. If you lowered the strings that much, possibly too much neck relief. Anyway, string may just be too close to the pickup which will cause weirdness

@ali_b - I solved it. Simple. Just added some additional dampening at the 3rd fret on the melody side. Now everything is behaving very nicely. I suddenly remembered seeing extra damper strips on some folks’ Sticks, and concluded at the time that it was for those using the Roland hexaphonic MIDI pickups and said “Duh…” :smile:

1 Like