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Out-of-phase signals in Creative Music Synth

Discussion in 'Electronic Basics' started by Radium, Mar 4, 2007.

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  1. Radium

    Radium Guest

    Doing as my research as I can this week, I still haven't found and
    answer to how this "illusion" is generated by cancelling the identical
    stereo signals. I've looked in detail about sidebands frequencies and
    FM theory but still don't have a clue as to how the out-of-phase
    signals are generated in CMS.
     
  2. Guest

    Dang I'm feeding the troll. OK Radium, take an average stereo
    recording (with center vocalist) in CoolEdit, invert the phase of
    either channel and then add them together. Presto, the vocalist is
    mostly gone. Fiddling with levels and timing offsets can achieve a
    nerly perfect null of the center field with all that remains being the
    _difference_ between the channels.

    As far as "identical stereo signals", there is no such thing. If the
    channels are identical, it's called mono (comparatively boring).

    What is CMS? Is it anything like PMS?

    GG
     

  3. ....an average stereo recording...?

    You speak from experience?

    Ok - take half a dozen CDs at random from your collection. Take a
    random track from each. There should be some "average" recordings in
    there yes?

    Now use the phase reversal trick, plus whatever further fiddling you
    like, to remove lead vocals. Post some short examples of the "nearly
    perfect null" you achieve.
     
  4. Rick Massey

    Rick Massey Guest

    Creative Music Synth. It's a program for editing sounds on a Creative Labs
    sound card. Radium is obsessed with this little program the company created
    a while ago, and for some unfathomable reason, has set this four operator
    consumer level synth as his or her gold standard for synthesis.

    For someone who works with professional level products, it is probably only
    slightly less frustrating than PMS.
     
  5. Radium

    Radium Guest

    Actually, Creative Music Synth is not a program.

    Creative Music Synth is the digital hardware chip-based FM synth
    present on the SoundBlaster 16 ISA card.

    Usually Creative Music Synth is set to an I/O address of 220, though
    in some PCs I've seen it at 240.
    Well, as I've in http://groups.google.com/group/sci.electronics.basics/msg/efc79a0c52cea68f?hl=en&

    Despite doing my own research, I still don't have the foggiest idea
    how the out-of-phase signals are generated in Creative Music Synth.
    Sorry if my persistence on this topic is annoying but I am insanely
    interested in it.

    Creative Music Synth does not -- to any extent -- playback samples
    from memory. It freshly generates its tones. It is physically built to
    generates its tones from scratch without stealing any energy from the
    PC's main CPU.
     
  6. Guest

    OK make it oldies. I just tried it on 'Saturday In The Park" from
    Chicago V. Nearly total null of vocalist. Carole King "I Feel The
    Earth Move" nearly perfect (estimate >-40dB) null of Carole. "Goodby
    To Love" by the Carpenters leaves the reverb portion of Karen
    Carpenter. "New San Antonio Rose" on the ride with Bob by Asleep at
    the Wheel also took out Dwight Yoakam. These samples were taken from
    the CD .

    GG
     
  7. Stuart

    Stuart Guest

    Another trick some music producers do to prevent vocal removal is to
    introduce a +/- 45 degree phase shift shuffle circuit. Couple with a
    shuffled and crossed reverb return prevents simple L-R circuits from
    achieving a cheap backing track. If you want to try it use Adobe Audition
    load in iZotope Ozone Plug-in.
     
  8. Stuart

    Stuart Guest

    Actually it might be easier to set up with Sonitus:FX plug-in as it has a
    preset fx for doing this
     
  9. Rick Massey

    Rick Massey Guest

    That might be the single most telling statement you've made about it. It's
    an obsession. Your resolve on this topic definitely eludes sanity.


    Which makes it exactly like a lot of other synthesizers out there. And
    sample playback on a soundcard is a truly different animal from sample
    playback in a professional synthesizer, which is one of the many places your
    tirade against them breaks down.
     
  10. Radium

    Radium Guest

    I am just really interested in those out-of-phase FM signals in CMS.
    How are they generated, if not intentionally by the designer?
    If a soundcard-based sample playback synth/soundfont/synth-emulation/
    softsynth has has a sample-rate, bit-resolutions, # of operators, # of
    voices, # of channels** that are at least a 100 times whats necessary
    for the average human auditory system to consider "music", AND [even
    more important!!!!!!!!!] the recordings are that of actual, high-
    quality, new, premium, clean, authentic, tradional instruments [such
    as piano, violin, flute, guitar]. Sigh...... Then yes, I am willing to
    give it a try and might actually enjoy it -- though, obviously not
    *nearly* as much as Creative Music Synth.

    But, unfortuntely, most soundcard-based sample playback synths/
    soundfonts/synth-emulations/softsynths don't have sufficient sample-
    rates, bit-resultions, # of operators, # of voices, # of channels**
    near whats necessary for the average human auditory system to consider
    "music". *More importantly*, the recordings are made from cheap,
    dusty, broken-down, poorly-conditioned instruments -- which is why so
    many sample playback synths/soundfonts/synth-emulations/softsynths
    stinks like the human kakaa they are. Ever listend to M$ GS
    "wavetable" synth? I feel like making and spreading a virus to infect
    that softsynth piece of s---.

    **Yamaha's OPL3 has 18 channels
     
  11. notejam

    notejam Guest

    This is slightly off topic, but the talk has made me wonder about
    keeping the vocals. Is that possible?
    I would like to keep the vocal information and remove band backing
    from analog and or digital stereo recordings.

    The reason I ask is band in a box now has a neat feature that can
    create a backing track to any vocal.. Sometimes it works pretty good,
    so it would be real nice if some one can create a vocal keeper program
    rather than a vocal remover, as a tool to use along with this feature
    in band in a box.
     
  12. Mr.T

    Mr.T Guest

    If you can successfully remove the vocal track from the original recording,
    the you should be able to invert the phase of that, and add it back to the
    original recording, giving you increased vocal instead.

    MrT.
     
  13. Stuart

    Stuart Guest


    Sorry it doesn't work like that - consider the algebra of stereo

    Left Total = Left channel info plus half centre channel (vocal) L+1/2C
    Right Total = Right channel info plus half centre channel (vocal) R + 1/2C

    Add them together and you get L+C+R = Mono

    Subtract either one from the other and you get (L+1/2C) - (R+1/2C) = L-R
    that is mostly the backing and it is a mono signal. R-L is exactly the same
    signal merely flipped in phase for one channel and sounds exactly the same.

    Now if you add or subtract this signal the L-R or a R-L from the L+C+R you
    can see you will never get a pure C. That's because it never existed as a
    discrete channel. Many have tried.... added to the fact that it is rare to
    get an absolute balance between the channels and the deliberate decision to
    fold in the reverb in a phase randomised manner...

    The best you can do with getting a clean vocal is to treat the signal as
    mono and then use a high pass filter to remove everything below say 120Hz
    and do the same above say 7 or 8Khz, then put a mid range bump around 3Khz
    and another one around 300Hz. By itself it will sound nasty but put an
    accompaniment behind it and you might get away with it. Has been done
    putting a new symphony orchestra behind some old acoustic records...BUT! a
    lot of work.
     
  14. Mr.T

    Mr.T Guest

    1/2C

    Assuming everything is panned hard left, hard right and centre.
    But for the point of the execrcise we'll ignore that :)
    Agreed, maybe that's why I simply said "increased vocal".
    If you reduce any part of L or R, whilst C remains untouched, then C *must*
    increase in comparison.

    MrT.
     
  15. Stuart

    Stuart Guest

    As you reduce the L-R level you move the signal closer to mono - if you
    increase the level of the L-R component to "increase the stereo effect" it
    reduces the vocal or rather any information that is common to both channels.
    The benchmark for the balance between centre channel apparent loudness
    compared to the backing is to listen to the total mix in mono. In practical
    studio mixing nothing much is hard left or hard right but in a locus defined
    around the centre line, especially if standard MS stereo microphones are
    used. XY microphones are even more diffuse and the ORTF parameters ( 2
    cardioids spaced at an angle of 110 degrees gives a superb spaciousness for
    large scale orchestral works or ambience effects but dreadful for soloists.

    In electronic music and midi based works then of course everything has to be
    panned into the desired place. In commercial recordings the maximum centre
    channel apparent loudness is set by monitoring in mono, once you switch to
    stereo the instruments left or right will start to effect the balance also
    the haas effect or precedence comes into play. So answering the op question
    " I would like to keep the vocal information and remove band backing from
    analog and or digital stereo recordings" is no it can't be done with normal
    2 channel stereo recordings.
     

  16. This isn't even theoretically possible by phase-reversal.

    Adobe Audition has a plug-in that uses various techniques to attempt
    what you want. It makes the best job of it that I've encountered yet.
    But, I fear, nowhere near good enough to extract a vocal clean enough
    for your purposes.
     
  17. Rick Massey

    Rick Massey Guest

    which is why so

    It's a soundcard. No one sane expects it to sound great. It is what it is,
    something for sound on a computer aimed at the consumer market. It's
    background for games and other multi-media applications. It's not designed
    for any serious work in real music synthesis. For that, get a real
    synthesizer or use csound.
     
  18. Radium

    Radium Guest

    Anyways, lets get back on topic.

    Doing as my research as I can this week, I still haven't found and
    answer to how this "illusion" is generated by cancelling the identical
    stereo signals. I've looked in detail about sidebands frequencies and
    FM theory but still don't have a clue as to how the out-of-phase
    signals are generated in Creative Music Synth.

    Please assist.
     
  19. Guest

    FM is crap and nobody cares except you. Get Gigastudio and get real.
    Let the flames begin.

    GG
     
  20. Rick Massey

    Rick Massey Guest

    You need a good understanding of acoustics and how wave interactions work
    before any of this is going to make one lick of sense to you. And in getting
    that grounding in the real theory of why this stuff works, you'll probably
    answer your own question.

    go find a good acoustics text book. A good freeware or shareware spectrum
    analyzer will also help you also, as will an oscilloscope program. With
    these tools, you'll probably find the answer to your question.
     
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