Bis is a Latin prefix or suffix designating the second instance of a thing, thus preceding ter. An example in recent modern usage is the ITU-T modem standard from the late 20th century, V.32bis. Bis can also refer to:
Pachelbel's Canon in D major, a piece of chamber music scored for three violins and basso continuo and originally paired with a gigue in the same key, experienced a tremendous surge in popularity during the 1970s.
The first chord appears to be the home chord or chord i. So the progression is best described as i-bVI and i/5 - bVI. Version 1. Version 2. This uses the progression Cmin-Ab major/C and Cmin/G-Ab major. the progression then modulates (changes key center) to Dmin-Bb major/D and sometimes Dmin/A-Bb major.