Moog Theremini Theremin

Removing instruments fromk backing tracks - Crazy technical idea floating...

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Posted: 8/11/2012 5:01:12 PM
From: Eastleigh, Hampshire, U.K.
Joined: 12/7/2007

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I am not sure if this is the right forum for me to float this crazy idea - and wish to also give warning that it is quite technical, and also may be completely impractical..

Over on the olympics thread the topic of backing tracks became quite dominant - I had not ever really thought about this "problem" - I have seldom wanted to play someone elses song, deluding myself by believing I am a composer (LOL) - and when I have wanted backing for a song, found a MIDI file, butchered it, and produced a backing that way..

However - GordonC put a link to "Hills of the North, Rejoice" and I love the arrangement of this song - none of the MIDI files I found were in any way usable, and it is  beyond my ability to produce a backing of the quality in that link.

So I have been fretting and pondering about how to remove the lead on that track - knowing full well that one cannot - its like trying to take the sugar out of a baked cake so that one can replace this with low GI Agave nectar..

Then I woke early this morning with a complete, and probably completely crazy, "solution". This "solution" uses the tools I have available - but (if there is any merit in it) could probably be tailored for other set-ups.

The idea:

Take a piece of music, load the audio file/s into a multi-track recorder, Ideally have a theremin which outputs CV, even more ideally your theremin outputs MIDI control data in CC format, giving CC for pitch, or you have a CV to MIDI converter which allows you to do this.

Play your theremin "over" the instrument you want to "delete" (or at least greatly attenuate) and record your theremin and the MIDI generated by it or its CV to seperate tracks in your multi-track recorder, so that both the music you are playing back (and playing along with) and the Theremin audio and (ideally) MIDI are in sync on seperate tracks.

Now - What you need to do is to feed the original music through a processor controlled by the theremin pitch - This processor would be a notch filter at least, which tracked the theremin pitch or MIDI data, and "notched out" the same frequencies from the original music.. This could be an external processor driven by MIDI or CV data from the recording of the theremin (one could, for example, just feed the recording of the theremin into a pitch-CV converter, and use the CV to drive a notch VCF, and record the output from the VCF back on a seperate track - and do this for both tracks of a stereo 'backing' seperately if one only has one VCF)

The above process could be repeated to remove harmonics from the instrumen one is removing, by tuning the VCF to succsessive harmonics from the instrument one is removing..

But ideally, I think it should be possible to develop a software "plug in" which could do the whole job simply by taking the recorded theremin (audio) track, analysing this (it does not need to be "real time" - so it could accurately determine the pitch without any constraints which bug real-time pitch analysis) and which could allow one to set the harmonic levels of the instrument to be removed, and process the original music in one 'hit' - one would then not need the theremin to output CV or MIDI, would not need a pitch-CV or pitch-MIDI converter - all you would need is a theremin and the ability to play the theremin accurately over the instrument you want to remove.

It might even be possible to make the "plug-in" a bit more intellegent - it could, for example, find the instrument in the original which was closest to the theremins pitch, analyse this instrument, and tailor its filters so that it tracked this instruments dynamics and harmonic content and almost completely removed it whilst doing minimum damage to other audio.

Alas, I have no expierience of developing audio "plug-ins" and this subject is well outside of my "comfort zone" - I will be looking into what is available in terms of development "kits" to see if I can do this job -

I would be really interested to hear from anyone who understands the above, and can see either flaws in the idea, or can point me in the right direction, or who (dare I hope?) has the ability and interest in developing such a plug-in or whatever.


ps - I have just downloaded both Cakewalk and Sony Direct-X  Plug-in development kits, I have visual C++.. now its down to trying to understand the darn monsterous collection of 'objects' one needs to work with, and the windows interface, and the maths - OMG.. there goes the next year of my life! ;-)


Posted: 8/14/2012 1:17:57 AM
From: Northern NJ, USA
Joined: 2/17/2012

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I haven't used it myself, but Celemony Melodyne might be the thing to try before reinventing a highly complex wheel.  There is an SOS review on it and several NAMM videos on YouTube (IIRC).  It looks quite impressive.

Posted: 8/14/2012 2:18:04 AM
From: Eastleigh, Hampshire, U.K.
Joined: 12/7/2007

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Hi Dewster -

Never seen " Celemony Melodyne " before - it looks unbelievable! They have a free 30 day trial, so I will try it!

£500+ for the full package or £250 for the editor - Ouch! - But I do understand - if it does what it seems to claim (splits  a composite track into its component parts, seperating out the instruments which can then be edited, deleted or whatever) then that is truly astounding, must have taken a huge expenditure in development, and the price is justified. (even if not affordable by those who just want to create an occasional backing track)


Posted: 8/14/2012 2:42:00 AM
From: In between the Pitch and Volume hand ~ New England
Joined: 12/17/2010

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We use Melodyne here in our studio. I'll be honest with you all, no singer is 100% on pitch. So when you have the right feeling and emotion but your are a nano sharp or flat on a note, Melodyne is a great tool!!! I mean, I take the time to sing all my songs as perfect as I can and melodyne maybe 2-5% of my vocals. Mostly to correct the drifts. It's a great tool too to harmonize, change a sequence or whatever... A valuable software that is for sure!

Posted: 8/14/2012 3:15:04 AM
From: Eastleigh, Hampshire, U.K.
Joined: 12/7/2007

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Am I correct in believing that Melodyne can not only correct pitch, but that one can select an instrument and delete it from the mix? For example, can one delete (or move to another track one can mute)the vocals (or other lead instruments) leaving a clean accompniment?

Im not too interested in correcting my pitch (its perfect! ;-) (LOL) - but I am interested in taking songs / instrumentals and splitting individual instruments / voices into seperate tracks - and also in producing MIDI files from these..

It seems to me that the whole "problem" of producing quality backing tracks would simply vanish by doing the above.. particularly if one produced MIDI and this accurately captured both pitch and dynamics, one could then use quality samples and recreate a backing modified to suite ones taste.

But, I suppose - if its just backing one wants, it is probably cheaper (but less versatile) to go and buy these - Reading the reviews, it seems one spends quite a lot of time tweeking the engine to get the best results - with £500 outlay and say 15 minutes per 4 minute song, one would need to do quite a lot of tracks (1500 @ £3 each) to recover your costs and pay you less than minimum wage for your time.

So I will collect together every song I may ever want to reverse-engineer, then download the 30 day free trial, and run this flat out for 30 days..

I also really want to see what it can do with Gordons album ;-) .. Now that will be a real test for it!


Posted: 8/14/2012 5:42:02 AM
From: Small town Missouri on Rt 66
Joined: 2/27/2011

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One might compare the cost of this cool whizbang software to, say what an electronics hobbyist buys.

I wanted to build great a sounding guitar amplifier cheaper than what Fender or Marshall sells theirs for, so I bought.....

Oscilloscope, multimeter, soldering station, ultramega dilithium core solder, variac, signal generator, drill press, table saw, laser printer to make PC boards, PC board blanks, PC board drills, CAD software, computer upgrades to run the CAD software, and enough parts and hand tools to sink a ship.

Oh, yea. That saves money ;-)

Posted: 8/14/2012 10:44:57 AM
From: Croxley Green, Hertfordshire, UK
Joined: 10/5/2005

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"I also really want to see what it can do with Gordons album ;-) .. Now that will be a real test for it!"

Especially the most recent one (Invisible Horn) which has faux stereo applied to most of the tracks, which works in a way that causes sliding tones to wander around the stereo field in a complex manner.

Which brings me to the point of posting - to mention the cheap and cheerful way of removing lead vocals from a song, which is based on the assumption that the lead is centrally placed in the stereo field, so can be nullified by inverting one track. There is a bit more to it than that, but the basic principle is phase cancellation. This is built into some low budget audio editors (Audacity springs to mind) and is also available in free VST plugin format. I gather that the results can be hit and miss, but at zero cost it may be worth trying before investing in a more sophisticated solution.

Posted: 8/14/2012 2:19:51 PM
From: A Coruña, Spain
Joined: 9/26/2010

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Anyone who releases a program that can remove the lead from a track without spending £500 and/or requiring lots of technical knowledge to tune the parameters will be my hero.

I like playing with backing tracks but don't have the resources to make my own. For some very well known tracks it's possible to free find backing tracks online, but for most songs it's impossible. Some websites offer a variety of backing tracks for a modest price, and I have bought some, but most of the time they aren't very good.

It would also be nice to create a section on this website to collect free backing tracks for thereminists. I would post the ones I've found.

Posted: 8/15/2012 1:09:49 AM
From: Eastleigh, Hampshire, U.K.
Joined: 12/7/2007

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"It would also be nice to create a section on this website to collect free backing tracks for thereminists. I would post the ones I've found" - AIK

Sounds like a darn good idea to me..

As I said earlier, I plan to collect the music I want to turn into backing tracks, and then download the Melodyne software (free 30 day trial) and process this music with it .. (in all likelyhood, if the software is as good as it seems to be, I will get myself even further into debt to buy it )-8 It will be a few weeks before I start to do this, and if it works I would be happy to post the backing tracks I creat that way.. Other people could then do the same and we could end up with quite a collection.

One thing I do not have any idea about though is the legal / copyright aspects of this process - If one strips vocals or other lead instruments from a track, does one bypass the originators copyright? I would be surprised if one does - I know if I was to put a track together and someone (with good reason, LOL ;-) was to strip my vocals from it and replace the vocals / lyrics with theirs (particularly if the lyrics were not to my taste or were offensive to me - like turning my song into an evangelical rant) I would be extremely peeved.

If copyright pertains, then this would probably kill the idea of having a collection here, as (if I understand anything about the latest legal stuff about hosting a site containing unauthorised copyrighted material) TW and its administrators could be prosecuted.

I suppose that this wouldnt apply to any music which is available free on other sites, and if only links (rather than actual content) was posted.

"Anyone who releases a program that can remove the lead from a track without spending £500 and/or requiring lots of technical knowledge to tune the parameters will be my hero."

I am still looking at the possibility of creating something to do this - but am moving away from doing it with "hosted" software ( I really find the Windows overheads and program structure extremely difficult - but worse, extremely, mind-numbingly boring.. this combination is what has always stopped me from getting deeply into windows before, and I think this time is the same) - thinking more along the lines of using an available DSP board into which one feeds a stereo signal and the theremins audio, and which outputs the input signal with frequencies in this which are close to the theremin frequency "notched out".


Posted: 8/15/2012 2:10:55 AM
From: Jax, FL
Joined: 2/14/2005

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Another device that has a center cancel feature is the Digitech Jam Man. You can run a signal through itand whateversounds are the same in both channels can be removed.


This will often take about bass and snare drum, too since they are often panned dead center.

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