Converting Mono to Stereo… For Real!

By Jerry Vigil

We’ve all played with “stereo enhancers” and “wideners” to try and get a stereo effect from a mono track, but none of these actually takes a mono piece of music, for example, and separates the instruments to allow for individual placement in the stereo spectrum. Think that’s not possible? Read on.

Ken Martin is the Program and Production Director for WTOJ in Watertown, NY. Ken also does work for Premiere Radio Networks converting old American Top 40 shows from the ‘70s that were done in mono into stereo for rebroadcast. Simple enough – get the stereo versions of the songs and replace the mono versions on the masters. But that didn’t fix the show’s theme song, which only existed as a mono version, and that wasn’t good enough for Ken.

The magic tool in his lab is a program called Spectral Layer Pro from a company with an appropriate name, Magix. Magix is probably best known in radio for their DAW Samplitude. (They also recently acquired Vegas from Sony and have many other products for video, web and graphics design.) Spectral Layer Pro will actually allow you to zero in on various instruments in a song and “extract” them. The various tracks can then be reassembled in your favorite DAW where you can process and pan tracks as you please.

Ken has performed this magic on two original AT40 themes and has prepared a video showing how he did it!

And if you’re interested in how he replaces the mono songs in the show with stereo versions, you’ll like this video tutorial:

Amazing! What I’m waiting for is what Spectral Layer Pro can do to a mono voice track. Is it possible to separate various frequencies of a voice and create a truly stereo voice track? I’ll be looking forward to see what else comes out of Ken’s lab.

Ken welcomes your correspondence at kenmartinaudio@gmail.com. Ken also notes there’s a whole website devoted to this technique at www.monotostereo.info.

 

Comments (2)

This comment was minimized by the moderator on the site

"Truly stereo voice track"? You're speaking with a forked tongue!

Music is often recorded in stereo to simulate the effect of a live performance (or even recorded in binaural, to capture a live performance). We're used to hearing instruments across the soundstage, so it makes sense.

But solo voices don't work that way. In fact, the frequency combinations in a solo speaking voice -- the bands you'd see on a spectrogram -- are what we hear as vowels! The vocal folds make a broadband buzz, at a pitch determined by the speaker's pipes and what they're trying to convey. The buzz is then filtered with various resonators formed by the shapes of the tongue against the roof and sides of the mouth, making a chord. While the actual pitch relationships are different, you can think of the difference between /ee/ and /oo/ and /ah/ as similar to the difference between major, minor, and diminished!

Want proof? Sing a note with an /ay/ sound. While you're still singing the same note, change it...

"Truly stereo voice track"? You're speaking with a forked tongue!

Music is often recorded in stereo to simulate the effect of a live performance (or even recorded in binaural, to capture a live performance). We're used to hearing instruments across the soundstage, so it makes sense.

But solo voices don't work that way. In fact, the frequency combinations in a solo speaking voice -- the bands you'd see on a spectrogram -- are what we hear as vowels! The vocal folds make a broadband buzz, at a pitch determined by the speaker's pipes and what they're trying to convey. The buzz is then filtered with various resonators formed by the shapes of the tongue against the roof and sides of the mouth, making a chord. While the actual pitch relationships are different, you can think of the difference between /ee/ and /oo/ and /ah/ as similar to the difference between major, minor, and diminished!

Want proof? Sing a note with an /ay/ sound. While you're still singing the same note, change it to an /oo/ and then an /ee/. You'll feel your tongue realigning for each, even though the fundamental note has stayed the same.

Want to try the effect of spreading the notes around a stereo field? Use a vocoder with panable outputs for each filter. [Don't know what a vocoder is? Well, you could read my books...]

I'd worry that if you actually separated the different frequencies, a) intelligibility would suffer, particularly for listeners who aren't centered, and b) talent's apparent location would jump all over the place, as they pronounced different vowels.

But hey, you're welcome to try.

For my money, the best way to make a single talent into a fully wide voice is Bob Orban's mono-compatible complementary comb technique from the 1970s. Still works like a charm. And if you center the bottom band, everybody gets a full, intelligible sound.

It's also a great way to take a vocal track in a musical performance and spread it wide, without having it in the center where it could fight with a voice-over.

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Jay Rose
This comment was minimized by the moderator on the site

Yes, I was speaking with a forked tongue, Jay! I was pretty sure it wouldn't be pretty if done, and you have pointed out exactly why, and offered two excellent options.

Ken actually ran Larry Morgan's voice track through the process and had this to say about my silly idea:

I don't know about that voice thing. You got me curious. If you don't select the fundamental frequency, but instead the 2nd frequency, the program highlights every other harmonic. Here's a screenshot of what that looks like. I just had to export this out and see what the results would be. I've attached that mp3 file. I'm sure you can solo each channel hear the individual tracks. One of them (the one represented in orange in the picture) almost sounds like a female! I'm sure Larry Morgan wouldn't be amused! HAHA

Here's a link to the audio: https://www.rapmag.com/files/archives/2017/03/Ken%20Martin-Stereo%20Voice.mp3

And here's the screenshot he mentions:
https://www.rapmag.com/files/archives/2017/03/S...

Yes, I was speaking with a forked tongue, Jay! I was pretty sure it wouldn't be pretty if done, and you have pointed out exactly why, and offered two excellent options.

Ken actually ran Larry Morgan's voice track through the process and had this to say about my silly idea:

I don't know about that voice thing. You got me curious. If you don't select the fundamental frequency, but instead the 2nd frequency, the program highlights every other harmonic. Here's a screenshot of what that looks like. I just had to export this out and see what the results would be. I've attached that mp3 file. I'm sure you can solo each channel hear the individual tracks. One of them (the one represented in orange in the picture) almost sounds like a female! I'm sure Larry Morgan wouldn't be amused! HAHA

Here's a link to the audio: https://www.rapmag.com/files/archives/2017/03/Ken%20Martin-Stereo%20Voice.mp3

And here's the screenshot he mentions:
https://www.rapmag.com/files/archives/2017/03/Stereo-Voice.jpg

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Comment was last edited about 3 years ago by Jerry Vigil Jerry Vigil
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