For the record, a Just Tempered scale is not a "Natural" scale--it is derived from a formula, based on the octave (2:1), the perfect fifth (3:2), and the major third (5:4)--a "natural" scale would be follow the Pythagorean series, which would follow the circle of fifths, the notorious "comma", which means that the last note in the series overshoots the first one by about 24 cents--the formula for the just scale was devised to work around the comma-

The just scale itself is not very practical for a couple reasons:

A) The C major scale features two different sized whole steps--the one from C-D is a bit larger than our whole step, and the one from D-E is a lot smaller--

B)The fifth interval between D and A is so far off that it is a noticeable dissonance--

C) Even the simplest key change, from C to G is impossible because the first three steps in the scale, C-D-E and G-A-B are not space the same way--(you'd need to have to change the pitch of A when you changed to the G)--

This is not to say that it is not possible to play and write music on a just tuned instrument--only that the type of melodies that we use most, which use horizontal chords and diatonic chord changes, will lose a lot of their lustre--

Modal music, such as is played on the pipes, or the multiferous droned stringed instruments, works just fine--

Actually, if you dispense with the need to change keys, and eighty-six all those chords (often in favor of a couple of octave/fifth drone notes) you can pretty much set the pitches for scale notes as your own taste dictates--

There are a a number of musical traditions where the pitch values are a matter of personal taste--who needs harmony? Melody and rhythm could keep you busy for a dozen lifetimes!