How hard would it be to make something like EHX's key9/b9/mel9 etc?

[Ruptor]

am I right in thinking that this may be what I was originally guessing? That it does FFT magic to figure out the actual notes (i.e., fundamental freqs) being played, then "reconstructs" those notes with the timbre you want? That's what I understood from "only has 6 fundamental freqs", anyway.

Yes it is a good question since a guitar can generate three fundamental notes an octave apart in a chord but midi guitar adapters seem to manage it and once you have the fundamentals it is easy to feed them through any effect or make them any instrument you want.

[deadlyshart]

A brief googling of the ADSP-BF592 says that it's only about $10, so price itself doesn't seem crazy, unless it needs some sort of crazy programmer.

I haven't done much research but it looks like the development software is about $1000 for a single user license, and a programmer is about $150. I've got no idea if there's cheaper or free alternatives.

ahhh, hahah, I didn't think of that... I wonder if there are open source options. Maybe I'll look into this someday, that mythical future time when I have some free time...

[markseel]

The FlexFX digital board layout is complete and ready for a prototype production run!

I'm planning on these boards costing something like $125?  It has plenty of DSP power but it only has the digital/DSP/USB - a separate analog board has to be connected via I2S and I2C.  The SDK and development tools are free.  The JTAG interface (if you want to override the provided SDK framework and write your own XMOS apps from scratch) is $20 from Digikey.

[deadlyshart]

So, brief update:

I caved and bought one! I bought the Key9 because after watching the various sample videos EHX made, it seemed like the one that had both the sounds I thought were coolest, and I could actually use in my music.

It's a ton of fun! I'll say a few things I've noticed already though, that I find very interesting...

For some of the presets, they won't play chords at all! It will essentially start freaking out, or alternating between notes of the chord you're playing. At least one of the presets, you can't even play two notes at once! And for the "steel drums" one (which sounds awesome regardless), if you even play single notes too quickly in succession, it seems to cut some out. Additionally, there seems to be a bit of noticeable latency sometimes. The manual mentions some tips for using it successfully, and uses the word "tracking"... this really makes me think that it's doing something like what I originally guessed, where it is figuring out what the fundamental you're playing is, and builds it from there.

Overall very fun though!

[potul]

Interesting... I have the C9, and this one is fully polyphonic in any setting...

[vigilante397]

I had the B9 for a while and it said it doesn't track chords very well, but it actually does

[anotherjim]

Probably the various kinds of these use slightly different systems. Hammond B9 was first & probably the easiest for EHX, basically it's a POG.

The most common Hammond sound is with drawbar values 888000000. That's 3 tones per note 16',5^1/3rd' and 8'.
16' and 8' are simply an octave apart, but 5^1/3rd' is a 5th interval in the musical scale (not the 5th harmonic). This harmonic is the pitch coupled from the 5th interval above the played key.  The error between the 5th interval compared to the true harmonic gives that characteristic sound. The organ tuning is the Hammond approximation of equal tempered tuning.

The 5th is slightly out of tune as a harmonic, but the higher "odd" drawbars are even more out (17th and 19th) so allow a metallic/bell effect. Other types of organ used similar method of creating the sound, although sometimes simple on-off switches for the footages instead of drawbars.

So if a POG is or can be set to create shifted pitch intervals equal to the organs scale, it's pretty close to getting the heart of it.
So I think that's the first step if you want to try it yourself.

EHX have denied there is any kind of tracking re-synthesis going on in the B9. I for one am inclined to believe it.

[llemtt]

https://aaltodoc.aalto.fi/handle/123456789/20158

My .02 is that at heart of ehxs is a "vocoder like" fft/filterbank processing where no "frequency analysis/detection" is performed (peak picking for instance shouldn't be counted as such...).

have fun

[llemtt]

Other bits:

"spectral morphing" is a keyword

chapter 11.3.5 of "Udo Zolzer - DAFX: Digital Audio Effects" shortly explains the algorithm

cheers

[pgiorgio61]

Wow... you guys know a lot about stomp boxes!
I'm an old fashioned engineer with some idiosyncrasies on digital world!
Anyway I have made some modifications on my B9 that maybe you'll like!
https://www.instructables.com/id/B9/
Please: be sympathetic with my basic knowledge and poor musical skills!