Invention 9 BWV 780 arranged for classical guitar duo in the key of F minor is a challenging invention to play particularly from the note reading and voice leading point of view. There are many accidentals to read and it is easy to make music reading errors. The arrangement is based on the original piano score with some necessary octave transpositions in place in the guitar 2 part. Guitarists have the option of reading either from a staff notation or TAB score attached to the full score A legato playing approach is required in the playing in what is a slow tempo and melancholy movement. In the sheet music score the ornaments are indicated but do not sound. The ornamentation in place is placed at the important cadence points in the movement. In the keyboard video score, which guitarists may wish to refer to on the PlentyMusic YouTube channel ornaments have been written out as they sound in the realisation to represent exactly what is being played. The realisation plays back at 58 quarter note or crotchet beats per minute. Accompaniments are in place allowing classical guitar players to participate in ensemble activities as part of practice routines. Classical guitar 1 sounds on one side of the stereo channel and the classical guitar 2 on the other. The accompaniment tracks play back at 52, 54, 56, 58, 60, 62 & 64 quarter note (crotchet) beats per minute. There is a two bar count in /click track at the beginning of the accompaniment tracks. Playing the music of Bach is challenging and his style is demanding and uncompromising in the consistency required to perform it accurately. As a composer Bach is not so much an innovator but one of those who brings all the musical elements of his time together and takes them to an altogether much higher artistic and technical level. The Bach Inventions are generally considered to be intermediate level movements when played on a keyboard instrument. The principle behind J. S. Bach’s two part inventions is to take a musical idea or motive and then process it following the rules of good contrapuntal writing using the compositional processes of the baroque and at the same time referencing the closely related keys in the key system. Inversion, repetition, sequence, transposition, rhythmic augmentation & diminution amongst processes are evident in Bach’s inventions as most other music of the baroque period. J. S. Bach composed 15 Inventions in a collection dating from 1723 intended to introduce keyboard players to composition techniques of the baroque. They are excellent ensemble movements.