This is a list of the ID's you will use to spawn items :

The command /spawnitem -IDGOESHERE-

IDs:
acousticbass
acousticsteel
electricclean
electricjazz
electricpick
slapbass
blownbottle
kapow
musicalgun
synthdrum
churchorgan
clavicord
drawbar
emotionalpiano
hardpiano
pdelectric
plelectric
rhodesmk1
sawtoothpiano
softpiano
sparksnewpiano
sparkspianosounds
steinwaygrand
sweettiddies
untitled
vintageupright
sparkpadatmosphere
sparkpadcrystal
sparkpadrain
choirvoices
halovoice
synthvoices
synthpadbasslead
synthpadbowed
synthpadcalliope
synthpadcharang
synthpadchiff
synthpadfifths
synthpadhalo
synthpadmetallic
synthpadnewage
synthpadpolysynth
synthpadsweep
synthpadwarm

flylofmradio
musicmachine
nightridefmradio
relaxfmradio
smoothjazzbox