I just did some quick tests. For every tier of the song, Minuet+2 added a total of 5 attack per song.
Miaa is mistaken, probably from using Soul Voice.
Despite the recipe below showing Goldsmithing first this is in fact a Bonecraft synth. If you are trying to HQ these you should base your chances off of your Bonecraft skill, not your Goldsmithing skill.