Since I have had it laying around for too long and considering there's no TPFC mention of it, I'm posting it for community consideration.
DFasma is both FLOSS and multi-platform (Linux, MacOS and Windows) but I can't really say if it's portable or not -- couldn't really test it, I always got an error saying some DLL was missing from my system (mainly 'easdif.dll') but I suspect the later, since there's only an installer package and the program is Qt based.
DFasma is a free open-source software which is used to compare audio files in time and frequency. The comparison is first visual, using waveforms and spectra. It is also possible to listen to time-frequency segments in order to allow perceptual comparison. It is basically dedicated to analysis. Even though there are basic functionalities to align the signals in time and amplitude, this software does not aim to be an audio editor.
DFasma last release is v1.0.74 and the downloading is a little more involved than usual:
You can download an installer with the latest updates by following this link (with FFTW3, libsndfile and SDIF support); then select your platform (x86 is for 32b Windows and x64 is for 64b Windows); then go under the 'Artifacts' tab on the right and select the executable file ending in .exe
Tried both x86 and x64. Did I miss something?