Separation Of Instruments

[Marc Hildebrant]

Group,

In the latest IEEE Spectrum Magazine (September 2009), is an interesting article (The Making of the Beatles : Rock Band) on an audio subject.

It seems that the people behind the "Guitar Hero" Software wanted to come up with a new game using all the Beatles songs. For the game, the individual instruments and vocals needed to be separated from the original audio songs.
The separate instruments sounds are needed to support the games ability to "judge" how well you play all (not something that I would want to do).
Anyway... the engineering challenge was to "pull out" the individual instruments from the original 4 track recordings. In the original early recordings, the vocals/guitar's would often be on the same track. Thus, they needed a way to filter the sound.

While the details in the story on just how they did this were not many, the article said that using analog filters to pull out the instruments didn't work and instead they using ~Audio Forensic Software~ that made it possible to separate and pull out each instrument from the total sound.

Any insight into if DC products were used ? Is it easy to do this ?

Regards,
Marc

[Craig Maier]

Hi,

I do not know if DC products were used. But, there are a lot of folks using our products and we do not know specifically what they are doing with it. This is especially true of the military and the various intelligence agencies around the world.

So, if I were to have been asked to do such a job, I would choose the highly selective and versatile Live/Forensics 32,000 Band Spectral Filter in conjunction with the High Precision Forensics Spectrum Analyzer to do that job. I would also recognize that the job would take quite a long time to accomplish, but is is certainly possible.


Regards,

Craig

[Marc Hildebrant]

Craig,

Sadly, much of the "how they did it" info was missing. So, to dig in some, are you saying that each instrument has a unique frequency domain signature that could be established and that that signature would then have a very detailed frequency filter applied ?

Would all the work be done in the frequency domain ?

Regards,
Marc

[Craig Maier]

Marc,

Yes, it would all be done in the frequency domain. If you download the free demo version of 7.5 and open the spectral filter, you will see that it has a number of very interesting modes (actually 4 modes) for separating out certain sounds. You might find Spectral Copy and Spectral Inverse to be interesting in this regard. Check it out.

Craig

[Marc Hildebrant]

Craig,

Tried the Forensics spectral filter out. Quite interesting indeed !
Removing/hearing just the voice was very effective. Focusing in on just an instrument will be some work though as the pre-sets are geared for voice (naturally).

Regards,
Marc

[Craig Maier]

Hi Marc,

Another very interesting mode in the Spectral Filter is "Spectral Difference". Les Paul and his audio tech were using that to match up optical tracks with magnetic tracks for given performances that were captured in both media. I think that "Spectral Difference" has a lot of possibilities besides that. One problem that we have is that often we do not know who exactly are using the various Forensics filters and how they are using them and the purpose or goal that they are seeking to achieve.

Craig

[Marc Hildebrant]

Spectral Difference

Craig,

Tried out the spectral difference filter. Quite interesting.....I took a "good" edison recording as a reference and then used the filter against a similar recording that was poor for the singing voice. The spectral filter improved the recording quite a bit.

Cool.....

Now, if you could just lower the price some.......

Marc

[Craig Maier]

Quoting Marc:

"Now, if you could just lower the price some......."

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I understand. But did you know that we are by far the most inexpensive Forensics audio systems out there? Most of our competitors start at $15,000.00 a copy to $25,000.00 on up.

And, these real expensive programs do not work as well as ours (not per our opinion, but customer opinions who have all of the softwares). Go figure.

Craig

[Dan McDonald]

which I guess suggests that you could take an old mono recording and essentially produce a multi-track version of it, then remix that for stereo, if you had the time and the inclination!

Dan

[Craig Maier]

Well, I never thought about that before, but it seems totally possible. It also seems like it could be quite a large task.

[Dan McDonald]

Yes, I think a huge task. You'd really have to have dedication to the project or a personal interest in the music (or find someone to pay you to do it).