Transpose means keep the steps and change the floor. The song still goes up a fifth at the same bar. It just starts on a different letter.
On ChordJoy the song address does not multiply. Amazing Grace stays one page. The key is a query on that page. Crawlers see the original. You hear the key you picked.
Fit your voice means the highest note you actually sing is comfortable. Ignore the name of the key until that note is easy.
Open a song, find the key control, and step it. The chart letters update. The pad updates. Fingerings update. If nothing moved, you are still on the written tonic.
Try Amazing Grace in G major, then in C major, then in D major. Sing the first line each time. One of those three will usually sit.
Auld Lang Syne and Ode to Joy are kind test pages because the range is modest. If all three keys hurt, the problem may be the octave you are choosing, not the tonic.
The path of the song stays. Bars stay. The feeling of I to V stays. Only the letter names and the diagrams change.
A pattern page works the same way. The Four Chords in C is C G Am F. In G it is G D Em C. Degrees are the stable thing.
A major and F major are farther jumps from G. Use them when C and D are still too low or too high, not as a first experiment.
Singers care about range. Guitarists also care about open strings. Sometimes the key that fits the voice is a barre forest on the neck. Capo is the usual peace treaty. The next guide is about that.
If you build your own loop, the chord progression generator lets you place letters in a key and hear them before you save. Nothing is uploaded.
Play When the Saints Go Marching In in a new key. If you still know the tune when the letters look new, the transpose worked.
Sing one pass with your eyes off the pad. If the form holds, the new key is yours to keep.
Save the key you liked in My Chords if you want it next time. The public page will still open in its written key for the next visitor.