%#(set-global-staff-size 32)  % it is scalable

grpnamesettings = \with {
  \override InstrumentName #'Y-offset = #(lambda (grob) (+ (system-start-text::calc-y-offset grob) 1))
  \override InstrumentName #'X-offset = #(lambda (grob) (+ (system-start-text::calc-x-offset grob) 0))
  }

instrnamesettings = \with {
  \override InstrumentName #'Y-offset = #(lambda (grob) (+ (system-start-text::calc-y-offset grob) -1))
  \override InstrumentName #'X-offset = #(lambda (grob) (+ (system-start-text::calc-x-offset grob) 0))
  }



\new GrandStaff \with { instrumentName = "Percussion I"
		      shortInstrumentName = "Perc1"
		      \grpnamesettings
	      }
<<  
    \new Staff \with { instrumentName =  "One"	
      shortInstrumentName = "1"
      \instrnamesettings
    }
    { s1 \break s1 }
    
    \new Staff  \with { instrumentName = "Two" 
      shortInstrumentName = "2"
      \instrnamesettings
    }
    { s1 \break s1 }

    \new Staff \with { instrumentName = "Three" 
      shortInstrumentName = "3"
      \instrnamesettings
    }
    { s1 \break s1 }
>>


\paper { left-margin=2\cm }