gistfile1.txt

records = [
    { id: "PU525", note: "Foo" },
    { id: "PU525", note: "Bar" },
    { id: "DT525", note: "Hello World" },
    { id: "PU680", note: "Fubar" }
]

[:id, :note].zip(
  records.group_by { |record| record[:id] }
    .map do |k, v| 
      [k, v.reduce('') { |memo, h| memo + h[:note] } ] 
    end
) # =>
# [[:id, ["PU525", "FooBar"]], [:note, ["DT525", "Hello World"]]]