Singing with a missing song

Singing with a missing song,
Humming, thrumming deep inside,
Mental engines screech along
Straining and complaining–wrong,

Wrong. Without a route decide
Which words best are heard beside
Others, difficult to build,
Intricate but meaning nil.

Rhyming, stymying my spilled
Thoughts I cannot make belong,
Words unsure they can be song,
Still they sing in what I've willed.