[Bard] Cantata of Soothing - No instrument mod?

[Eugee]

L34 Bard Song (Velious) - Reads that it gives 5 mana/tick, requires Lute.

So I have a Lute of the Gypsy Princess (x2.1 effect or +1.1 effect), and my friend is watching his mana climb: 1259, 1265, 1271, 1277

He's only getting 6 mana per pulse (1 natural and 5 from song), is the instrument not not applying correctly perhaps? We did both tests standing to eliminate that variable.

EDIT:

To be thorough, I wounded myself then played Cantata, and checked the HP regen: 966, 975, 984, 993, 1002. The song gives 4/tick, so this looks like it's being boosted by the lute correctly, but mana is not.