gradual progress: music changes from weak (sometimes slow) to normal speed and intensity

gradual progress: music gradually slows down or weakens from normal speed (intensity)

gradual progress is usually used in the introduction or prelude of music or songs, and gradual progress is used at the end or termination of music paragraphs.

The gradual emergence of strings is more, because the expressions of strings are more abundant. Usually a bow, or a melody will gradually fade out.

gradual fade-out is also called fade-in and fade-out in MIDI editing. The meaning is the same