Click on the keyboard to activate it. Click on the keys to play tones.
Use the number keys 1 thru 9 to play chords.
This is a keyboard that plays notes from an 8-tone scale. I think this is the sort of scale that is used in Javanese music.
Compare this to the Western scale below. (Sorry about the absence of black keys…but that’s really not my point here.)
Notice that there are some tones common to both scales, but that there are tones in each that aren’t in the other.
To make chords sound good, the tones of both scales are arranged so that the ratio of the frequency of one tone to that of the next is constant. This isn’t the only way to produce a scale, but the arithmetic is quite simple.
Various cultures have made music with various sorts of scales. The Western scale is nice, but it is not intrinsic to music.
By the way, I found out why Western keyboard instruments have seven white keys and five black keys per octave: the modern Western 12-tone scale is composed of two earlier Greek scales, one with 7 tones, one with 5. The key colors reflect that history.
Problems with Keyboard Applet.
You might also search for related material in the Encyclopaedia Britannica.