Pitch & Key
Scale & Key Reference
Pick a root and a scale to see exactly which notes are in play. For writing melodies, basslines, and chords that stay in key, or for setting your synth's scale lock.
How scales work
A scale is a pattern of intervals, a fixed recipe of steps, applied from a root note. The major scale is whole-whole-half-whole-whole-whole-half; start that pattern on any of the twelve notes and you get that key's major scale. Minor scales, modes, and pentatonics are just different step patterns. That's why the same shape transposes to every key: you're moving one pattern up and down the twelve notes.
In practice
Knowing the notes of your key is the fastest guard against sour melodies: stay inside the scale and everything is broadly consonant. Many soft synths and MIDI effects have a "scale lock" that snaps every note you play into the chosen scale; enter the root and scale here and you can set that up to write freely without hitting wrong notes.
The modes are worth exploring once major and minor feel comfortable. Dorian (minor with a raised 6th) sounds minor but hopeful, and it's huge in house and funk. Phrygian and Phrygian dominant carry a dark, Spanish or Middle-Eastern flavor that suits a lot of techno and cinematic music. Pentatonics remove the two most dissonant notes, which is why they're nearly foolproof for improvising a lead.