Lync and Skype for Business shipped two separate hold files:

  • DefaultHold.wma, installed with the Office client under Office15\Media. The client plays it when you put someone on hold, unless a policy points somewhere else.
  • cpsmoh.wma, used by the server-side Call Park service when a parked call has no custom music.

Both are WMA files bundled with the product. Microsoft doesn’t name a composer, so there’s nothing we can legally play here.