In addition to Frequency Shaping, the ability to raise and lower the volume in sections is crucial to making professional-sounding recordings. In live recording situations it is not uncommon for bands to have some balance problems between instruments, particularly if there was insufficient time for a sound-check. When a guitarist or keyboardist switches in an effect there can be volume jumps. When a saxophonist switches to flute there can be volume jumps. All these situations, and more, are encountered in most live recordings. And by the way, not a few studio productions as well.
Making Room. Of course the first and most basic “volume shaping” you’ll want to do is to highlight the whole song by double-clicking on it, then going to “Amplify” and cutting the overall volume by -6dB or -12dB. This gives you the headroom to adjust the dynamics or frequency shaping without going into clipping and damaging the waveform. In digital editing－unlike analog editing－you can make as many changes as you want like this without introducing any noise or distortion. When you’re all done editing, then you do your normalize and compression back to 0dB.
Fades. The beginnings and endings of each track must be zeroed out using “Fade In” and “Fade Out.” If the waveform is not at zero amplitude at the beginning and end you will hear pops when the file plays. This fade can be very fast, only a half dozen samples are needed, so it will not be audible when playing two songs that run together. This process of zeroing out the head and tail goes by all sorts of fancy names on bootleg forums (such as “zero-cross alignment”) but it’s really nothing more than making sure you have no lingering voltage at the end of a file.
Adjustable Fades. There is also an option in Audacity called “Adjustable Fade.” Instead of going from 0 to 100 (fade in), or 100 to zero (fade out), you can specify the beginning and ending amplification. This very handy if there’s a section of the song that’s too quiet; you simply highlight the beginning of the low passage through to where the volume catches up, and set Adjustable Fade to fade down from 140% to 100%. Repeat the process until the sections flow together smoothly. Or if you have a soloist who is totally out of balance with the band, highlight the middle of the solo to the beginning of it, set Adjustable Fade to fade down from 100% to 70%, then repeat the process in reverse from the middle of the solo to the end. Once you begin treating the audio file as clay to be molded, you’ll find yourself playing musical conductor as much as audio engineer.
Spot De-amplification. Sometimes, before you ever get to normalization and compression, you’ll have bass drum hits or cymbal crashes that are WAY out of whack. You can highlight these－making sure to start and end your highlighting on zero-crosses－and give these whacks a 3dB or 6dB cut. Conversely, if the drummer lacks zest, sometimes it’s advantageous to BOOST the kick drum or snare drum, beat-by-beat. Luckily you can try all this stuff out and if it sounds unnatural, simply go to Edit – Undo. Audacity is limited only by your disc storage on how many layers of undo you can have.
Once you save (or export) a file though, you lose all you undo options.