In addition to major scales, the improviser has several other scales from which to choose. The scale which includes every key of the piano, black and white, is called a chromatic scale:

Another much-used type of scale is the harmonic minor scale, used to improvise on a minor chord or in a minor key:

Still another form of minor scale is the melodic minor:

There is also the diminished scale:

And the whole tone scale:

And the five-tone pentatonic scale (This is the scale which is used all over the world as the basic tonal background of much folk-music. It is equivalent to playing all the black notes on the keyboard, and no white notes.):

Then there is the Alexandrian scale, very popular around the Mediterranean area:

And the blues scale, derived from combining our Western diatonic scale with the “blue notes” sung by Black slaves and their descendents in the South:

In addition to all these scale possibilities, we can also form “modes,” based on the centuries-old church modes.

If we started on C and went up to the white notes to C, we would be in the Ionion mode (identical to our major scale):

But if we started on D and went up all the white notes to the next D, we would have the Dorian mode:

What makes the modes sound different from one another is the fact that a different scale is produced as the intervals between the white notes vary in occurrence.

Here is the Phrygian mode:

And the Lydian mode:

And the Mixolydian mode:

And the Aeolian mode:

And finally, the Locrian mode:

These modal scales can originate on any note, of course, not just the notes we used above.

So when a musician improvises a melody, he has all these scales (and others) to use, combine, and experiment with.