If you rather like “peaceful” yet “rich” sounds, you may well prefer ... Bach’s orchestral suites and Brandenburg concertos

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Sushi: I would disagree. I'm somewhat of a Bach fanatic, the Brandenburg Concerti are hardly "peaceful" -- for example, Harnoncourt's Brandenberg, with the celli and the harpsichord pounding away, sounds more "rock" than "baroque"; but yeah, the Mozart (yawn) is very "peaceful"

Spiffnme, the "problem" in this case is really, the piano didn't exist until the 19th century, and by that time music has become quite romantic (i.e. not peaceful); and the cello was also used more as an accompaniment than as a solo instrument until that same time. The music you're looking for may be in short supply (but of course, I may have misunderstood).