Just for fun I just played with Audacity for concatenating audio files. I used Pink Floyd's Dark Side Of The Moon as a test. Doing it one way, by opening all 10 tracks and then cut and pasting them, it took me about 5:20 to do everything. About a minute of this was opening the files and about a minute was exporting the big concatenated file at the end
Then I tried the method of choosing "import" from the file menu on all 10 tracks at once. That opened the tracks as separate audacity tracks in the same window, as opposed to individual windows in the previous experiment. Instead of cut and paste, I used the time shift tool to move each track to the end, and then on to the next track, moving it to the end. I didn't know that tool would "snap" to the end, which it does. This made it very, very easy to concatenate the songs right up against each other with no gaps and no overlap. Total time for this, including all the importing and the big export, was about 4:10.
So not slow, not super duper fast. but not too bad for building and saving 43 minutes of audio. Definitely a viable method if you don't have more than a few albums or a couple of dozen tracks you want to process. Different story if you have dozens of albums or hundreds of tracks.
Brian.