(Correction: audacity is done in C++, there is no Pascal...)

sox is The sound editor focused on doing everything from command-line. This means that you can do all the work from bash scripts etc. For example this bash command will take all *.wav files in current directory and generate 2x louder versions in louder/ subdirectory:

for FFF in *.wav; do sox $FFF louder/$FFF vol 2.0; done

See http://sox.sourceforge.net/