There is a tradition of Jazz concerts in the Monferrato area.
If you are around in June, there are going to be three concerts in Treville, organised by the council and taking place in the village square, overlooking the hills of the Monferrato. These concerts are on Fridays and on the following dates:
6th of June
13th of June
20th of June
If you are thinking of having a meal before or after the concert, I would recommend the "Ristorante dell'Opera" in Ozzano (2 miles from Treville) or "La Rata Birata", a wine bar that also serves food in Treville (200 yards for the concert area). They have completely different styles, but both worth a visit. L'Opera is a more traditional restaurant and you can also find some truffle dishes most of the time (although the famous white truffles are mainly in Autumn).
The other place where you can enjoy live jazz music is "Le Cave di Moleto", where every Thursday night you can have a traditional dinner at their restaurant (with really lovely wine) and then stay for the jazz concert. This happens throughout the year, with the difference of the location, i.e. it is inside a renovated barn in winter and outside in Spring/Summer time.