Do not judge only by the highest note
Some songs do not go very high, but low notes or long phrases can still make them unstable. A good key fits both range edges and breath demand.
The original key may not fit your voice. To choose a key, first test the low notes, high notes, and longest phrases that tend to cause trouble, then decide whether to transpose up or down.
Use Piano to find the song's rough lowest and highest notes, then verify stability with Pitch Monitor. If the top note is only touched once and immediately falls, lower the key. If the low notes disappear or turn breathy, try raising it.
Some songs do not go very high, but low notes or long phrases can still make them unstable. A good key fits both range edges and breath demand.
Touching a note once does not mean the song fits. A controllable note is repeatable, not squeezed, and does not collapse at the end.
For practice, lower the key if needed. Stabilize the hard phrases first, then move closer to the original or performance key.
Use Piano to play the lowest and highest notes, then sing each softly three times.
Check whether the curve stays around the target instead of jumping up and falling.
Use Scale Ladder to test step by step and note today's stable upper and lower limits.
No. A fitting key makes pitch, breath, and tone more stable. You can challenge higher keys later as ability grows.
Not always. Voice type, training level, and daily condition all matter. Judge by actual low notes, high notes, and long phrases.