The idea is to use the Lyre to quickly rebuild a town after a dragon attack. We just ended a campaign during which a town was attacked by a red dragon and the GM asked us what our characters want to do in the time after the final fight. My idea was to give a Lyre of Building as a permanent loan to the town council because he is attached to the town and wants it rebuild soon.
Interesting question. :)
After a careful reading of the item I'm afraid I have to say it's not possible to use it to generate raw materials, as the descriptions clearly specifies building stuff:
... magically construct buildings, mines, tunnels, ditches, etc.
So the wood have to be chopped and worked by hand, but once it's made into suitable planks etc. then it can be used by the Lyre.
The only thing I'm a bit uncertain about is the mining, and I think it'll have to be up to the DM how much the Lyre does in this case. It is specified that it can be used to construct a mine, but what happens with the stone and ore removed in this process is not detailed. Taking the general intent of the Lyre, I'd say that the stone and ore would be gathered in a pile outside of the mine, ready for actual workers to separate and process the ore. As these things are not a part of actually constructing a mine, but rather the (usual) reason for why a mine is constructed.
As usual it is the DM that's the final arbiter on what's possible or not to do with the Lyre, depending upon how widely he defines the act of "constructing" to be.
There is nothing in the description of the Lyre that permits it to do something that is not building or labor to do so.
Quarrying stone and making planks separate from building is not building.
Quarrying stone and building with it is building.
The stone and trees are a form of raw material, just less processed than cut blocks or finished planks. The lyre would be capable of quarrying said stone into blocks, transporting it to where it is needed, and connecting the stone together.
It wouldn't just quarry the stone and leave it in a pile, or make planks and stockpile them, as that is not building. It would cut down trees, make them into planks, and build the planks into a tower or a cabin.
It will do the work of 100 laborers over 3 days. The labor-price of everything it does must all be paid for; cutting of trees, dragging of logs, pounding of foundation.
An easy way to work out how much it builds over 30 minutes is to use the professional income system. Untrained laborers generate 1 sp per day of labor, and professional laborers generate (skill check/2) gp per week.
A +4 check laborer earns an average of 1 gp per day of labor.
So the Lyre generates between 300 sp and 300 gp of building value per half-hour of play. Raw materials delivered to the site would reduce the amount of work it would have to do by their value.