I recently worked with a DJ who remixed an early 80′s song. There were two transitions from the remix to the original song which was a low quality, mono mp3 file. So when the song played the original parts, the previously wide and dynamic sound collapsed, it sounded thin and grainy.
First I tried to revitalize dynamics and match the frequency curve of the different parts. Then I split the original parts to 3 frequency bands and applied a short 10-12 ms left-right channel delay on the highs. And so it sounded awful… Although this technique often works fine with individual tracks this time it did not. The original parts did not have enough clean air to work with and even worse, the instruments and the vocals just did not come apart.
I thought it once again and found a very simple yet wonderfully working solution. I routed the original parts to two different busses. On the first buss I made the required dynamics and EQ adjustments so the samples sounded bigger and cleaner. On the second buss I set up a tempo synced stereo delay 100% wet, and processed the echos to sound smooth and clean with a weak low end. I turned the volume fader all the way down and then started to slide it upwards very slowly. At a very low setting the mix started to sound quite fine. The original samples had the same punch as the newly produced tracks and a nice stereo width without hearing any echos distinctively. Job done!