The accompaniment instrumentalists and/or singers can be provided with a fully notated accompaniment part written or printed on sheet music. This is the norm in Classical music and in most large ensemble writing (e.g., orchestra, pit orchestra, choir). In popular music and traditional music, the accompaniment instrumentalists often improvise their accompaniment, either based on a lead sheet or chord chart which indicates the chords used in the song or piece (e.g., C Major, d minor, G7, or Nashville Numbers or Roman numerals, such as I, ii, V7, etc.) or by "playing by ear". To achieve a stylistic correct sound the accompaniment pattern should remind or imitate the original version using similar rhythms and patterns.