Once you reach level 70 your instruments will change, you will have a basic instrument, Battle-Singer, Wary Watcher, Resolute/Resolve, Harmony, and Conservation to choose from. These are crafted by a woodworker and the rough stats of each instrument are as follows:
Exquisite Premium
Exquisite Premium Lute of the Resolute
Exquisite Premium Flute of Harmony
Exquisite Premium Flute of the Battle-singer
Exquisite Premium Flute of the Wary Watcher
Exquisite Premium Flute of Conservation
After your level 70 instruments there are some changes to the instruments again, still with the same names however. Your instruments are available at 70, 85, 95, 115, 120 and 130. These below are the 130 instruments available to you.
Minas Ithil Flute
Minas Ithil Flute of the Wary Watcher
Minas Ithil Flute of Harmony
Minas Ithil Flute of the Battle-singer
Minas Ithil Flute of Resolve
Minas Ithil Flute of Conservation
Each minstrel has a choice as to what instrument they prefer, as that is one thing that is so great about LotRO is how many different ways you can build your minstrel. The common theme however is most choose Resolve to heal with and Battle Singer to use for solo play for the most damage.