Polyphonic MIDI?!

The G2M™ Universal Guitar to MIDI Converter.

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joso1958
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Joined: Mon Feb 02, 2009 1:30 am

Polyphonic MIDI?!

Post by joso1958 »

I understand that the G2M is monophonic, but is sonuus planning on releasing a polyphonic guitar-to-midi converter!?!? I would buy the g2m in one second if it was polyphonic. Also, why couldn't you guys have made it polyphonic? (I actually want to know - I'm not an expert on MIDI and I'm curious as to why it couldn't be made polyphonic)

THANK YOU!
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james
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Re: Polyphonic MIDI?!

Post by james »

We can't publicly talk about products that haven't been officially released, so we can't say if we will be releasing a polyphonic version or not. I can, however, say that our technology will allow this in some form.

There are two types of polyphony and they both have problems:

(1) Using a hex-pickup to separate the output of each string so they can be processed independently. This works very well, but the physical setup of the pickup can be tricky and of course you need the special pickup.

(2) Without a special pickup the audio can be processed and chords extracted. The problem with this is that latency is increased because you need to measure the signal for more time to be able to resolve the different notes. It is also difficult to reliably detect notes which are harmonics of other notes, for example. So, although this can work reasonably well, you don't get the low-latency that most users demand, and the accuracy of note conversion may not be perfect (it might sound OK, but if you are using it to transcribe chords it could miss notes).

The above problems are some of the reasons for the G2M: keep it simple to use (no special pickups, or other configuration parameters to tweak), keep it low-cost, and ensure it has low-latency.
drg
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Re: Polyphonic MIDI?!

Post by drg »

I don't see a problem here - all you need is to combine in one G2M device... 27 (frets) x 6 (strings) current simplified G2M-like modules to recognize each note and a one transpose feature for a bass guitar.

Well, if you will add here a little computer - you can convert to MIDI all the guitar techniques and styles.

The advantages of such approach - virtually ZERO latency, no needs for special pickups and conversion any sound/voice to MIDI.
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james
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Re: Polyphonic MIDI?!

Post by james »

I'm not sure what you're saying here...

The biggest problem with latency for polyphonic signals is basic physics, particularly when you are trying to distinguish two tones that are close together in frequency. As two frequencies get closer together you need a longer time before you can be sure you actually have two tones. No additional computing power can get around this.

Even your brain experiences this, but it is clever enough to mask the latency and make you think there is zero latency.
drg
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Re: Polyphonic MIDI?!

Post by drg »

When two tones are close together in frequency, they anyway can be easily distinguished without a PC. I saw it was done by a boy about 40 years ago... Of course his device had ZERO latency and worked accurately... It's the matter of the algorithm, not physics - just make it VERY simple... (to eliminate latency).

In the most expensive scenario you can hire, for example, a programmer who works/worked with EEG (brain rhythms), ECG (heart rhythm) and the like. Accurate-zero-latency-sound-recognition (making MIDI files) is not a hard task as it looks like. If you cannot resolve the problem the way you know - try another approach.

It doesn't matter if a programmer is a musician or not - all you need - give him a properly formulated task, which he could understand... Of course, you need to find a creative one... Why am I so sure? I worked on the similar project - it's all about the algorithm... Some programmers are not able to find a simple solution when they analyze complicated wave-forms and due to this they offer bulky unreliable solutions, others - can find the key-pattern and give you exactly what you need.

The sounds, which are between..., also can be recognized as a note (to the closest one) or, for example, as the guitar glide (depends on the settings). I just don't understand - why this is a problem...
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james
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Re: Polyphonic MIDI?!

Post by james »

If you have a solution to this, then great, send it to me and we'll hire you. Or maybe you should patent it!

But you won't be able to get beyond the limitations of the physics (unless you have a time machine or something similar).

Absolute zero-latency is not physically possible. You cannot measure the pitch of something before you have measured that it is oscillating -- that is the minimum latency. Just the same way as you can't measure the speed of something without measuring the distance it has travelled over some time (you can get small, but never zero).

But, in practical terms, latency can be small enough to be either unnoticed (perceived zero-latency) or small enough to not be a problem (your brain easily compensates for it). The latter is particularly noticeable if you play electric guitar. There is a lot of latency as the sound travels from the amplifier speaker to your ear, but you compensate for it and with practice this feels like "zero latency", when it can be several ms.
drg
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Re: Polyphonic MIDI?!

Post by drg »

Of course absolute zero-latency is not possible in the meaning of absolute. I am talking about the practical meaning of zero-latency. For example, who will notice a delay if it is less than 1/3,000,000 sec?

I told you that the best solution is pretty simple (just hardware) and with the help of modern PC, it could be a perfect one (it's relative, of course).

Potentially I can help you with it, but I am not in this field now and it could take couple of months before I will come to a working solution. The problem is I am overloaded now. Thus, you need to find another one who can think beyond standards.

I'll repeat it again - the solution is simple, and the only stoppage here - it is not the obvious/typical one.

Wish you the best.
rcf
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Re: Polyphonic MIDI?!

Post by rcf »

The G2M demos impress; the mono unit seems to track very well, with minimal latency. I will definitely purchase a G2M, and I would happily buy a polyphonic unit, even if latency was increased. Polyphonic pitch extraction from a mono input is, I appreciate, very complicated. I have used the Lateral Guitar Synth software , which does allow this - latency is poor but acceptable for laying pads etc. A small, reasonably priced portable hardware unit would definitely get my vote.

I'm very interested in drg's claims, but also very sceptical. I simply don't believe you could ever achieve the claimed latency figures with mono pitch to midi, let-alone polyphonic pitch to midi from a mono input device. If he can find a working solution in two months, then I'd happily help finance him.

Maybe he is right though, there's some very clever stuff going on with Melodyne's Direct Note Access software.

;)
joso1958
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Joined: Mon Feb 02, 2009 1:30 am

Re: Polyphonic MIDI?!

Post by joso1958 »

wow, thanks for the replies guys! I feel like i just got a physics lesson from all that lol
rcf
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Joined: Fri Feb 13, 2009 1:38 pm

Re: Polyphonic MIDI?!

Post by rcf »

Our product roadmap includes plans for other innovative pitch-to-MIDI products like the G2M, ...
;)

I have a GI-20 for use with my 13 pin synth ready instruments- this take care of my needs for poly pitch to midi in the studio. However, I would love a mono in, polyphonic Sonuus G2M product. It would be portable (hopefully, still battery operated), and I could use any of my electrics to drive it. With a suitable laptop/netbook and a couple of vst's, I could play anywhere!

Should such a product be developed, would it have a mono/poly switch for increased accuracy with a mono input? A usb output would also be useful, for getting midi into a laptop/netbook without exra fuss.

RCF
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