Restoring Golden Age Tango Music

- Doug Reuhl


I began my career in 1974 selling Stereo equipment. Those were the days of the reel-to-reel tape recorders, high quality phonographs, receivers that weighted 80 pounds, and large good sounding speakers. I was quickly hooked and spent lots of my earnings buying the best audio equipment of the time. That passion for high quality music reproduction has stayed with me for more than 40 years. In 2008 I was introduced to Tango, the music grabbed my heart and my mind immediately. Its layering, its nuances, its unique sound, I fell in love with it. So after listening to tango music, with all its noise, distortion, clicks, crackle and limited frequency response, I thought there must be a way to make it sound better. That led me to learning about music restoration. I purchased my first piece of restoration software in 2012. I have spent thousands of hours learning how to use it and its subsequent versions, to get the most out of every tango. I thought you might enjoy knowing a bit more about the process.

The resurgence of Tango in the 1980’s brought renewed interest in the music, dance and culture of Argentine tango. Most of the re-mastering of golden age tangos occurred in the late 1980’s through the early 2000’s. This reproduction process had intended and unintended consequences. On the bright side we have a large variety of Golden Age tango music available! On the dark side, many sound dull and noisy.

The master recordings for most tangos recorded before 1955 are no longer in existence due to a variety of technical, financial and political reasons. Without a master recording when a studio makes a CD it is making it from a previous recording, usually a Vinyl record. Re-mastering in this period had the consequences of adding reverberation to disguise harmonic distortion and loss of frequencies to hide noise. Reverberation is stretching of tones creating an echo effect and was the best method for masking the harmonic distortion, but creating an artifact in the re-recordings. Noise at that time was removed through equalization, the adjusting of volume by frequency. This often led to all music above 10kHz being cut out completely, sometimes the cuts occur as low as 6kHz. The result is a loss of the original sound in the studio. Often a studio would re-master and then throw out the original source recording. The noise, distortion, reverberation, volume imbalances and missing music of commercial CDs leave our ears tired and our impression of the beautiful music feeling old.

The vitality of this beautiful music may be restored!

Music Restoration
Music restoration has come a long way since most Golden Age tango CDs were produced. I work with the best restoration products currently available; the 2014 Grammy Award winning iZotope RX4 Advanced and its companion Ozone 6 Advanced. With these products I apply a mixture of science and art bringing beloved old tango recordings back to life.

Side by Side comparison of “Rosamel” performed by Carlos Di Sarli,
recorded in 1940, restored by Doug Reuhl



Commercial CD

Shellac Digital Direct Transfer

Restored from the Shellac

You can hear some noise, clicks, pops and skips, in addition it sounds “hard” or harsh.

Much more noise, but the sound is more realistic.


The realism remains of the Shellac remains, the vestiges of age are removed, more music is present, and the sound is in stereo, resulting in a sound that is more alive and real.



Click here to hear the difference!


Starting the Restorations with the Best Source Material is an important first step.
Shellac recordings are the closest source to the lost original Masters. Shellac is better than Vinyl because it could record a greater frequency range more accurately. They are also more fragile, rare and expensive. Shellac direct transfers are also noisy, filled with clicks and pops, and because they have had a needle dragging through their grove high frequency is usually compromised. If you listened to a direct transfer from a Shellac you would deem it unplayable at a milonga because of the noise and distortion. Even in this condition they contain more music and material to work with for music restoration and fewer artifacts than in Vinyl.

I begin the music restoration process by de-clipping the recording. Clipping is waveform distortion caused when the volume attempting to be recorded overloads the recording chain’s ability to record it. In the Golden Age of Tango, 1925 to 1955, technology was rapidly evolving. Electric recordings began around 1927. Studio recordings until the mid 1940’s consisted of one microphone with the orchestra surrounding it. The singer would stand directly in front of the microphone and many times sing so loudly and be recorded so closely that clipping would occur. Digitally eliminating clipping, rebuilds the clipped waveforms removing the distortion you hear from many singers in tango.

Removing Clicks, Pops and Crackle
The next step is to remove clicks, pops and crackle. Clicks are usually minor imperfections on the surface of the Shellac or Vinyl. These are random occurrences. There are also periodic clicks caused by scratches in the surface of the recording. It is not unusual to find more than 10,000 of each type of click in a recording. Listening to clicks causes ear fatigue and distracts from the music. Pops are more significantly damaged areas in the recording caused by micro-cracks in the surface. These usually need to be removed one at a time by the restorer using a spectral repair tool that interpolates the music on either side and fills in the missing music while removing the unwanted pop or thump. Crackle is a form of extended clicks much of which exists in frequencies above 7 kHz. This is the harmonic distortion we hear in so many tango recordings. It sounds like a high frequency vibration and is the most fatiguing sound of all. Thoughtful setting of the parameters of on the de-crackle tool can remove much of the crackle.

Removing Hum
It is common for Tangos to have 50 Hz hum with up to 8 harmonics. This sounds like a low frequency rumble or buzz, again very fatiguing and often quite loud. These sounds are completely removed, unmasking the string bass, allowing the beat to be easily heard.

Removing Noise
To remove noise from a recording, it is important to have a good noise sample that doesn’t contain music. Happily, direct transfers from Vinyl or Shellac leave in the lead-in and lead-out sounds of the recording so these noise samples are easy to obtain. These samples are not available on most commercial CDs making the de-noising process harder. Once detected the software looks for that noise signature and removes it from the entire restored recording. The result is stunning! The noise is gone, leaving only the music behind.

Restoring the Harmonics
Music in its primary frequencies ranges from 1 to 4,180 Hz. Additionally each note has a harmonics associated with it. The harmonics are simply multiples of the original notes. So, 50 Hz harmonics are 100, 150, 200, 250… On an analog recording each frequency is recorded as a vibration pattern in the grove of the disc. Higher frequency waveforms are the smallest vibrations hence are the first to be worn away. The recording technology of the Golden Age was not capable of capturing all the harmonics a listener would hear. Using harmonic excitation, harmonics are reproduced from the original frequency and placed where they have been lost. This brings a fullness and richness back into the music that simply had been lost through wear or the deficiencies of older recording technology.

Balancing the Dynamics
Prior to the mid 1940’s there was no standard for equalizing the music being recorded. The microphone and the Shellac or Vinyl that it was being recorded onto changed the volumes at the different frequencies being recorded. It was up to the studio to rebalance this. Sometimes because of time, taste and equipment this was not done well. Using the dynamics module the tonal characteristics of the music can be rebalanced to match the sound that was taking place in the studio at the time of recording. This module also allows the restorer to use digital compression to address the muddiness of the bass typical in older recordings removing artifacts caused by the technology of the time. The restored bass will sound natural and tight.

Dynamic Equalization
In spite of being able to rebalance the dynamics there are certain frequencies that may remain out of balance. Violin harmonics are one that I frequently notice. Dynamic equalization allows the restorer to lower or raise the volume at a particular frequency but only if the volume reaches a particular level. For instance the violins in some Biagi’s recordings may sound harsh at certain points. With dynamic equalization that harshness can be softened without interfering with other instruments that have harmonics in that range.

Making Mono into Stereo
We hear sound in stereo and we are used to listening to stereo recordings. Stereo recording began in the mid 1950’s at the end of the Golden Age so most of the recordings we listen to were recorded in mono. Until recently making a mono recording into stereo inserted annoying and disorienting phase shifting. Today the technology for “stereoizing” music can be accomplished without this problem. Stereo imagery makes the music sound alive, real and current.

Equalized Volume Levels
How do you prevent the D’Arienzo from blasting your ears and the Callo from not being loud enough to bring you to the dance floor? This is not quite as simple as one might think. Some tangos have very little difference between their quietest and the loudest passages and some have a lot. So how do you volume equalize so they all sound about the same in a milonga? The recording industry came up with an algorithm to address this. It is called LKFS. I am using the most recent version released in August of 2012. LKFS requires a lot of modern computer processing power. My 2014 Macbook Pro takes 25 seconds to calculate the proper adjustments for one tango. Once set the volume levels of each tango match. Unless I made a mistake you won’t hear volume differences between the tangos that are played.

Every tango I play has 5 seconds of silence at the end of it. A consistent amount of silence gives you a chance to breath between tangos in a tanda. It is a small detail but you will appreciate the time.

In 2014 Madison Tango Society invested in a beautiful pair of FBT EVO2MAXX 4A, 12” two way powered speakers with 400 watts RMS for each woofer and 100 watts RMS for each horn, producing flat frequency response across the entire audible range. We use a Focusrite Scarlett 2i2 USB Audio Interface to connect the computer to the speakers. To get the smoothest most accurate reproduction of the music from my computer I use Amarra player, the industry leader in digital audio output. It is rare to find a sound system this good at any milonga.

It takes between 30 and 120 minutes to restore a tango; not counting the time it takes to procure it. If we use the low end of that time range, the typical 4-hour milonga contains 76 tangos, which require a minimum of 38 hours of restoration. It is a lot of work, but as you know the pursuit of the best audio reproduction possible has always been a passion of mine.

Hear all of the nuances possible in this beautiful tango music, in stereo, with no noise, no distortion, no volume variances, consistent time between tangos, and finally, hopefully, a good selection of tangos to motivate you and keep you dancing. This is why I think the best sounding Golden Age Tangos are found right here in my restorations played at MTS milongas in Madison, Wisconsin.


Doug Reuhl