UniversalNextTrack.scpt

if appIsRunning("Pandora") then
  tell application "Pandora"
    activate
    tell application "System Events" to key code 124
  end tell
else if appIsRunning("iTunes") then
  tell application "iTunes" to next track
end if

on appIsRunning(appName)
  tell application "System Events" to (name of processes) contains appName
end appIsRunning

UniversalPlayPause.scpt

if appIsRunning("Pandora") then
  tell application "Pandora"
    activate
    tell application "System Events" to keystroke " "
  end tell
else if appIsRunning("iTunes") then
  tell application "iTunes" to playpause
end if

on appIsRunning(appName)
  tell application "System Events" to (name of processes) contains appName
end appIsRunning