Audacity – WAV Merge
This is not something I did for my Smuggler Bill project, but I have put this post here because I can imagine some people who are into this type of hobby might find it useful. I can also see myself in a couple of years time needing these techniques for editing a movie sound track and not being able to remember how I did this, so this is also here to act as a reminder to me.
Have you ever had two recordings of a piece of music, which were identical, but each had imperfections in different places? Wouldn’t it be great if you could combine the good parts of both recordings to make a perfect or at least much better recording than either of the originals?
I have used Audacity for this because considering it is free, it is an excellent and versatile piece of software.
Click on the images below to see larger versions
In this instance the situation was slightly different. I had two recordings of a piece of music I love on different CDs, the problem is that they had been mastered differently.
First I converted both copies to WAV files and imported them into Audacity, by selecting Project / Import Audio… If you look at the two sets of stereo waves above you may see some similarity. The problem with the top stereo pair is that middle passage is far too quiet. Of course I could amplify that part, but was concerned that some of the fidelity may have been lost. The bottom pair is very loud at the beginning and the end. Some audio clipping seems to have taken place, which does nothing for the quality of the sound.
So what I really wanted is the loud sections from the top Wav file merged with the quiet section from the bottom wav file.
Having opened both sets of Wav files, the first step was to make sure they both had the same amount of lead in silence. i.e. from pressing play, they would both start playing at the same instant. I deleted a bit of leading silence from one of the files, so they both started playing simultaneously.
I then scrolled down to the end of the files and noted that one finished slightly earlier than the other. It was only a few seconds in a ten minute piece of music, but it meant that the two sets of Wav files would get progressively more out of sync as music played.
Even when zooming in really close it was difficult to see where they both went totally silent, so I chose a slightly earlier, but more distinctive part of the waveform to try to match up.
The goal now was to align the wave form of the bottom Wav stereo pair with that of the top Wav stereo pair.
I shortened the second wave by speeding up its tempo slightly. Effect / Change Tempo… If you use change speed, instead of change temp, then the pitch will also change. Using change tempo, keeps the pitch as is.
I used the percent change. It took a few goes of changing the tempo and then undoing the change and trying again before I got it right. The image above was taken when I tried 1%. In the end I settled on 1.12%. Obviously this would be a good time to zoom in really close to ensure the waves match exactly as possible.
The next step was to silence the bits of wave that I didn’t want to hear. I selected the part of each wave that I wanted to disappear and selected Edit / Silence. I kept a bit more of the too loud WAV than I need to create some overlap.
I then selected the first part of the middle section Wav and picked Effect / Cross Fade In and then selected the end part and Effect / Cross Fade Out. Again it took a bit of trial and error, of selecting different lengths of the wave and applying the Cross Fade and using Undo, before I got the result I wanted.
Having played back the result and made some further adjustments, I then selected File / Export as WAV…
Having closed my working files, I opened my newly merged Wav file.
There it is. I am very happy with the result. I now don’t have to leap up and down to adjust the volume of my stereo mid song. I will admit that to the trained ear there is a tiny amount of echo detectable at the Fade in / Fade Out points. That is down to my impatience to get on with it. I should have zoomed in a some more and taken more care about alignment, but funnily enough, I quite like the effect, and I’d be amazed if anyone else ever notices it.