I can't really tell you much but I'll try, I'm better with Quarter Horse lines..
I don't really know a whole lot about the Musing, I can find information saying he was a hunter but not much else, he does go back to Bold Ruler on his 4th generation. Bold Ruler was the sire of Secretariat also, Bold Ruler was known for his speed but couldn't last in the longer distance races..Musing also goes back to War Admiral (4th Generation) and Man O War (5th generation) Both are/were really awesome horses..
Here are links to more information I found about him. Musing xx - Thoroughbred Stallion Musing Horse Pedigree