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 A minor chord iv is the D minor chord, and contains the notes D, F, and A. This subdominant chord's root / starting note is the 4th note (or scale degree) of the A natural minor scale. The roman numeral for number 4 is 'iv' and is used to indicate this is the 4th triad chord in the scale. It is in lower case to denote that the chord is a minor chord.