A scale is a series of notes arranged from low to high according to a set rule. It is a map for writing melodies and for when you are unsure which notes to use. The C major scale, for example, is the series of white keys starting from C.
Scale versus key
A key is the idea of the central note of a song and where the song lives. A scale is the concrete set of notes that work well in that key. In the key of C major, you can build melodies and accompaniment based on the C major scale. If a key is where the song comes home to, a scale is the set of paths you can walk along the way.
Common scales
The first ones to learn are the major scale and the natural minor scale. Major tends to sound bright and settled, while minor often feels calm or wistful. The pentatonic scale, narrowed down to five notes, keeps your options tidy and is handy when you are starting to write melodies. There are many others, including blues, Dorian, and Lydian.
Using scales in a DAW
Some DAWs can dim notes outside a chosen scale or correct notes that fall outside it. Choose C major before entering MIDI and your options are narrowed to the equivalent of the white keys. Do not leave everything to correction, though; checking against the chords and with your ears matters too.
Relationship to chords
Stacking notes from a scale gives you chords. Line those chords up as the flow of a song and you have a chord progression. Even within the same scale, which notes you lean on and where you return to changes the impression. Writing a short melody using just one scale is a good way to get a feel for its role.
Tips for learning them
Before memorizing theory, pick a key from a song you like and play the scale notes on a keyboard or in the piano roll. Comparing them with notes outside the scale lets you understand by ear why the series is useful. A scale is not a restriction; it is a starting point for writing.
