The speed back and forth, is determined by the banjo players desired effect and ability to control the pick. A variation to the melody tremolo is to tremolo any string of the chord being held. This latter technique is a good starting point for improvising. When Chord Accompaniment and Single String Melody are combined and played simultaneously, they become what is known as Chord Melody style playing. This technique consists of playing chords that have the song melody note as the highest note.
Inversion means another location for a chord, and different finger positions.
Any chord finger form can be moved to play lots of other named chords up and down the banjo neck. It is a simple concept and well worth the effort to learn. This technique is an enhancement of the Chord Melody technique. The tremolo can be performed on any string while holding a chord. A tremolo can go back and forth across one string, two strings, three strings, or all four strings, depending on the desired sound.