On the heels of President Barack Obama breaking into "Amazing Grace" during a eulogy, a well-meant but embarrassingly uninteresting musical depicting the life saga of the hymn's writer has opened. Watching it, you keep thinking, "How in the world did this get to Broadway?"

Although it culminates in a beautiful choral rendition of the title song, the rest of the score is by former police officer and Broadway novice Christopher Smith.

John Newton (played with vigor by Josh Young) is a young 18th century English merchant whose family business is the slave trade. In the musical's most chilling moment, newly arrived slaves are brutally pulled out of a cage for a public auction and then branded.

Somehow or other, Newton is plucked away from his virtuous girlfriend (a pouting Erin Mackey) and disapproving father (a starch Tom Hewitt) and conscripted into the navy, accompanied only by his slave Thomas (the characteristically excellent Chuck Cooper).

Not soon after, Newton is shipwrecked and becomes the prisoner of an African princess, who uses him to build her own slave-trading operation. Eventually, he comes back to England as a newly enlightened, songwriting abolitionist and man of the church.

Resembling an old-fashioned adventure novel, "Amazing Grace" is packed with changes of fortune, sentimentality and one-dimensional characters. Smith's mushy, forgettable songs sound like the work of someone who loves "Les Miz" but has little talent of his own.

The workmanlike production (directed by Gabriel Barre) pulls off a visual coup at the end of act one, using a flying effect to show Newton on the verge of sinking.

Too bad they couldn't just sing "Amazing Grace" at the start and save everyone 2 1/2 hours.

If you go: "Amazing Grace" plays an open run at the Nederlander Theatre. 208 W. 41st St., amazinggracemusical.com.