minor scale systems

[renfroejames]

Hi,
I was wondering if someone could explain to me why the harmonic minor scale is played the same way whether it is descending or ascending, while the melodic minor scale ( with raised 6 and 7) is played ascending but the natural minor is played descending. 
Also, let’s say I was composing an ascending melody using the melodic minor scale – do I need to use specific notes going up but vary them going down? My confused logic would say yes because I need to play the natural minor while descending.

[indianajo]

Scales are useful for training your fingers, but composers have not felt limited by them since the end of the nineteeth century or earlier.  The twelve tone movement didn't even stay in a particular key.  Certain runs derived from scales are more common in bluegrass or jazz music, or vamping standards out of a fake book as a pianist.  Take the minor scales as a way of training your ear and fingers, not aids to composing. 

[renfroejames]

Your reply helped me to define my question a bit more. I guess what I was asking was how classical compositions from around Bach to Beethoven used the minor scales.

I understand (I think) that the last 150 years have really departed insofar as composing is concerned from time of B to B. I am mainly trying to understand how music was composed then in order to understand what things have changed over the last 150 years.

All theory I come across on Jazz, Bluegrass, or whatever always frames explainations by "what changed" - I am trying to gain understanding how devices like the minor scale system was used before the change if that makes sense.

[indianajo]

There were certain conventions in playing of the early days that were useful to professional musicians playing in groups.  The most obvious example is the "credenza", a part of an early piece that was left blank that real artists took as license to fill in something artistic and new.  In those days, the improvisation had to fit the established conventions or be hooted down.  Similar but different conventions have built up now around jazz, rock etc.  Arrangements in the early days were not totally spelled out, since everything had to be copied by hand, musical shorthand was very useful.  As published scores became more common, the arrangements were filled out and the knowledge of the player was more piece specific than just a general cultural canon.  I have not taken college level music theory, it sounds as if you have the curiosity to make such a course worthwhile for you. I do know what I like, and pieces that follow the historic conventions are more pleasing to my ear usually than pieces that flout them.  I find Schoenburg (?) and followers of his twelve tone school tedious and boring no matter how loud they are.  Oddly enough, masters of the historic scale and chord relationships have mostly moved out of the classical orchestra into the realm of popular music, especially "rock" and "pop". (There are modern orchestral composers that use chord structure, but they are usually segregated off to the "pops" orchestra and looked down at by the over-educated).   The move of pop away from the piano to the guitar had more to do with the economics of pleasing  a crowd and splitting the money 4 ways, instead of 60 ways, than with any musical defect of the piano.