What matters is the characteristics of the sound, not the way it is produced. A synthesised sound (like the ones used in the article) will have a more or less definite impression of pitch depending on the pattern of frequencies it contains. Of course, not all music consists of "playing tunes" and there is a wide range of sound options, both physical and electronic, which are used in music and are not covered in this simple article. But for a "tuned percussion" sound, the computer needs to be given a recipe like those discussed here.