One that would teach you concentration, that way you have no need to watch it successively.

Ascending on any instrument is to play successively higher and higher pitched notes.

Descending would be playing successively lower and lower pitched notes.

Stable, well adjusted, simultaneously, concurrently, successively...

Rutherford and Soddy's theory stated that uranium successively disintegrated to lead. Rutherford discover the proton. He also discovered that the atom is mostly space.

bed sheets, dark places