A computer intended for audio production doesn't need to be of the top-of-the-line kind, but you'll of course get better performance from a newer and more capable computer. Basically, anything fairly modern will work.
I personally use one stationary Core i3 540 at 3.07 GHz with 8 GB RAM running at 1333 Mhz, one laptop with a Core i3 M 330 at 2.13 GHz with 4 GB RAM and finally one netbook Intel Atom N550 (dual core) at 1.5 GHz with 2 GB RAM at 667 MHz and a SSD instead of a traditional HDD. With any of those I can record without any problems, but especially the noise reduction is best done on the laptop or stationary. If I try it on the netbook I'll test my own patience to the limit. On any of my computers I can without any problem run GrandOrgue, but the memory/cpu of the netbook of course limits what samplesets can be loaded and how many samples can be played simultaneously.
If one uses windows there are a multitude of audio editors to use, most notably Sony SoundForge which of course is not free. On Linux the choice is somewhat limited. I'll try to specify what software I use for each purpose. Previously I used Wavosaur quite a lot running through Wine, but since I discovered that it degrades the wav files with each open and save I've stopped using it.
- Recording. For this I use a normal version of Audacity that comes with the distribution. Great care is needed to get the settings to be correct. Also it's good to make sure that all recording devices except the mics to be used are turned off. Especially built in mics and stereo mix if that's available should be turned off to lower noise.
- Cutting the recorded stops into octaves for better noise reduction can also be done in Audacity. Just make sure that the audio settings that the application works with and the export settings match the originally recorded file's, or even better use only 32 bit floats from the first time you open the original recording in Audacity until you're ready to finally export the individual files.
- Noise reduction is done with Nick Appletons NoiseReduce, currently the 0.15b version.
- Eventual resampling, bit conversion, cutting and exporting into single note files named like 036-C.wav can also be done in a normal Audacity version. Again be careful with the settings, especially set dither to none to avoid extra noise artefacts introduced until the feature gets fixed.
- For looping and marking one can use Nick Appletons Autoloop (currently 0.3b version and you'll have to ask Nick for Linux executables) for batch processing the files with shell scripts (possibly run simultaneously in different terminals to make the most of multi core computers). Later the loops and cues can be assessed (and edited or even created) in my own software LoopAuditioneer to select the good ones (remember that GrandOrgue will need multiple loops to overlap at least one other existing loop) for saving. Now with the more recent releases of LoopAuditioneer it's possible to autosearch for good loop points within the GUI with nice possibilites of controlling all the loopsearch parameters. This works in both single file mode and in batch mode. I've put together a short user guide for LoopAuditioneer on the Sourceforge hosted webpages that I recommend anyone interested in using the software to read.
Of course if you decide to use windows instead there are many easy (and sometimes costly) alternatives to use. But Linux is my preferred platform, so I'll keep trying to have fully functional tools for sample production on it!