Twelve notes. That's the entire alphabet of Western music, and once you can see them laid out, everything else — keys, scales, tuning — suddenly makes sense.
One step between each = one semitone. Twelve steps = one octave, and you're back where you started.
A semitone is the smallest normal step in Western music — the distance from C to C#, or from E to F. Two semitones make a tone. That's genuinely all the maths you need to read any scale chart, including the ones on our scale and key finder.
A chromatic slide is that delicious half-step creep that makes a line feel like it's climbing towards something. Soul and R&B singers use it constantly for runs; film composers use it to make you nervous. Because it belongs to no key, it works as spice anywhere.
Chromatic tuning allows all twelve notes, so it only ever nudges you to the nearest one — very safe, very transparent. Diatonic tuning knows your key, so it can push a properly flat note back into the song instead of leaving it half-wrong. Start chromatic if you're unsure, then set the key once you know it.
You can try both right now in the free browser vocal tuner — no install, no signup.
Twelve. Every semitone between one note and the same note an octave higher — C, C#, D, D#, E, F, F#, G, G#, A, A#, B — and then you're home again.
Neither. It has no key centre and no built-in mood, which is exactly why it's used for movement and colour rather than for writing a melody.
It's the safest default when you don't know the key, because it never forces a note that isn't in the recording. But once you set the real key, corrections sound noticeably more musical.