You will need to have a good source (audio oscillator) to drive the equipment that your 334A will analyze. If the source has poor sinewave quality, such as from a general purpose function generator, then the THD readings of the 334 will quantify that.
If your computer has a decent sound card, then a software based audio generator can make a very low distortion audio source, and have all kinds of bells and whistles.
I use the Dr. Jordan software:http://www.dr-jordan-design.de/index.htm
They have a free downloadable neat audio generator with some of the DSP features disabled. Here is the link to download the file directly: http://www.dr-jordan-design.de/Download/SigGen.zip
You can run two of these at the same time for two tone testing. Running into a laptop speaker, can surely irritate family members, and the house cat too.