That's it. Can the exemplar use this magic item.
The Exemplar gets an ability like bardic performance, but it does not use music. It does say that feats and effects that effect bardic performance effect the exemplar's ability.
Three Reasons to Live is a musical instrument that gives a significant bonus to bardic performance.
If a bard uses the horn to start a bardic performance,
I read this as the user needing to use perform (wind instruments) as their performance.
Instead of the Perform skill, she activates this ability with impressive flourishes and displays of martial talent (this uses visual components).
So no, IMO.