Crossbows and bows have to be constructed out of parts that relate to how high the base force can be, then just raise the max velocity and allow string parts to exert different force strengths (say that adamantium for being both light, nigh unbreakable and thread like is perfect, gcs and forgotten beast thick webs being second to some kind of metal fiber wire alternative) if the material can take the wear and tear.
Urist pulls the trigger on his new crossbow, and the shiny filament of Adamantine jumps forward... neatly slicing through the bolt which barely moves from its perch. Urist then gives up on this new-fangled marksdwarfship and uses the crossbow at it was intended: a blunt melee weapon.
Real modern crossbows use springs to hold the projectile in place and carry through the tension created from the string to push foward larger arrows such as bolts (just breaking or colliding with the arrow at risk of splitting for no movement as you describe being a product without the spring when the projectile is too heavy) assuming that dwarven crossbows use a similar method, or deliberately 'round off the edges' of the adamantium/lubricate/use some kind of precise mechanical stopping block to receive the force without being cut. Dwarves naturally probably have this planned out mechanically so their crossbows are a different design to ours, perhaps having a few different mechanisms such as a wind up cog so that dwarves do not have to touch the dangerously sharp adamantium wire.
Remember the idea is to just use the tension to propel, so literally anything a dwarf could design is in bounds (sliding rollers, a small metal gear stop to physically shot-put arrows like a minature golf club for example as long as it delivers it to the desired place)
Thats the reason why nobody used 'bolts' as we know them in the 15 century, too heavy to be propelled by a string alone even at high velocity by later renditions of more powerful crossbows (bolts are entirely metal in the DF universe, and also because of weight, with poor power being shot out of a crossbow added with the weight it flies less far).
So can anyone point me to a good discussion/tutorial about the new musical instruments and making some sanity of them?
They are procedural, the best answer i can give is to look up artistic renditions of them (look for the completed instruments on the 'objects' panel of details for a detailed description of what they play and are made of) generally they will be made out of multiple materials but they all follow a usually quite similar theme. Sometimes you'll get a doddly easy peasy stone pipe, and other times some monsterous organ made out of glass, ceramic and bone besides obscure materials, all depends on the world and how it generates.