Use of the cello as an accompaniment instrument - here's an interesting article: Cello Accompaniment Concepts in Traditional Music. The range of a cello is C to E, similar to the viola, but an octive lower. It doesn't lend itself very well to melody in traditional music, which is in the range of the fiddle - G to B. But it is great for chordal bass lines.

Cheers, S. in Seattle