Somebody out there to help me with putting accidentals? They are valid during the measure and only for the octave. But is there some convention to follow (upwards all sharps and downwards all flats)? Or is it just a matter of readability? Please point me to some reading material.
The harmonic chromatic scale is as follows:
using c as an example:
(no degree of the scale has more than 2 notes and neither tonic nor dominant can be altered).
however... if it looks neater and tidier to write accidentals in a different way than do it like that. in beethoven's concerto in g he writes the chromatic scale in 4 different ways! this is sometimes called expedient false notation.
Every note can be written in more than one way. These alternative ways of writing a note are called spelling and two different spellings of the same note are called enharmonic equivalents.
Which of the enharmonic equivalents of a note you should use depends on the purpose of the note. Every piece of music has a key signature that defines which spellings are "normal" for that piece (if there is more than one key signature, you can consider each fragment with a given key signature separately). If you need to write a note with an accidental, the usual implication is that the note defines the position that the pitch occupies in its scale and the accidental modifies that pitch upward or downward.
Here's an example. Suppose you have written a piece in C major and your first four notes are C, B, C, and G. In this case, the C represents the first step in the scale, the B represents the 7th step (or the 0th step, if you like, because I intend it as the B that's adjacent to the C), the second C is again the first step of the scale, and the G is the fifth.
Now, suppose those four notes appear later in the piece, but transposed up a fifth. The first note therefore becomes G, the second either G-flat or F-sharp, the third G, and the fourth D. So should it be G-flat or F-sharp?
The answer is that the first two of these four notes represented different steps of the scale when they were in C so they should represent different steps when they are in G. In other words, becuase the first note is spelled as G, the second note should be spelled as F-sharp, not G-flat, becaues it represents a different step of the scale.
So: To decide how to spell notes, think first about whether it is possible to play in a key that makes your accidentals vanish. Then use the accidentals from the signature of that key.
More generally, to decide how to spell a note, you have to understand the purpose of that note.
Andrew and others, thank for the replies. Now I understand it. But looking at some score, sometimes I have the feeling that the editor used and accidental because it looked smoother and clearer amongst other notes.