Two. Chord direction selected when arranging. It is not the same thing as the later harmony recording.

Three. Mixing is the last step. Post processing.

Four. You can't.

Choose a song. . Choose a good song that suits the singer.

Set the tone. . Generally according to the singer's own range.

MIDI arrangement This is a process of making samples. Of course. And it's all MIDI arrangement. Not a recording instrument.

Musical instrument recording. . The previous arrangement is for musicians' reference. It may be played as scheduled. It may also be some personal performance of musicians. It depends on the producer.

Mix. . That is, the processing of audio tracks. And the mixing process of all the tracks.

Master tape processing. . The mother of record burning