screaminside wrote:1- if we are using a key say a( a minor ) or whatever then we have to use only the notes in the scale and never use other notes out side the scale ? i found some song use notes from out side the scale
2 - is there harmony between two musical scales played at the same time ?
3 - is there any ways to change from a key to another while playing the same song
1. Yes, you can use notes from outside the scale. In a general sense, you can use any note at all. There are no notes that can't be used. You just have to know how to use them. Knowing how to use them means understanding, either consciously or unconsciously, the relationship that any particular note has with the key of the song, the current chord, the previous notes and also the style of the song.
As a simple example. If the key is C major, a non scale note is F#. It can be used as a passing note very nicely between the scale notes F & G. It can also be used to emphasise the 5th (dominant) scale degree G, (because it happens to be the leading note of the key of G). Another non scale note is Eb, which is one of the things that gives blues its bluesy sound. So context is important, too. If you want a bluesy sound, then use it as much as you like - but not so much that it sounds like a cliche. The b7 note Bb can be used to give a bluesy sound too, and can also be used to emphasise the 4th note of the key, F.
Don't think in terms of CAN or CAN'T. Think in terms of CAUSE and EFFECT. Every musical decision that you make has consequences. A good musician makes good decisions with good consequences.
2. Two scales played at the same time time will always produce harmony, but not harmoniousness. In other words, unless you're very aware of the effect that that would produce, you're unlikely to get the harmony you want - unless of course you're experimenting with 'uncharted soundscapes' and want to combine C major with C # melodic minor, to make a style of music never before heard in your neighbourhood.
If two scales blend completely well, then they are probably just the same scale counted from different notes, e.g., C major and A natural minor.
3 Only if the key of the song also changes - otherwise, why would you want to?
Coolnama - some good info there. A couple of corrections (as you asked)
The relative major of A minor is C major, not C# maj and A major and A minor aren't modes of each other.
Not sure what you're asking about the dominant. You mean use the scale of the dominant key? i.e in Am, you'd use the scale of E major or Eminor? - Same question as above - "Why would you want to?"
Yes - you'd get access to possibly interesting notes that are foreign to the A minor key, but if you already know what those interesting notes are, just use them anyway, in addition to your A minor scale, when the situation calls for it. If you don't know what they are, then you'd soon find them if you used that scale, but you'd have to learn how to use them safely first before letting them loose in a solo in A minor.