Dedicated electrical lines

Your house is at least 140 feet long? I’m impressed. The material alone for three 140 ft-plus circuits is almost $500 if you buy it yourself.

What the job will cost is hard to say. Depends if the electrician is going to do the carpentry work.I am assuming there’s space above the ceiling instead of the sheetrock being tight to the roof joists. If so, then the job is impossible without tearing down a swath of the ceiling the entire length. And then each joist has to be drilled for each of the three circuits, and going through insulation.

140 ft? It would most likely be less expensive to add a 30 amp sub-panel close to the music room. You could run a single 6 ga Aluminum or 8ga copper line to there and then 3 shorter lines to create the circuits. It would also leave you room for more circuits at a much lower cost per circuit in the future.
That solution would also leave available one more slot you have in your existing main panel in case you need new circuits to originate there.

That’s not 140 ft in a straight line. It’s 50 to one corner and then 90 ft to the room.
 I have a 50 amp line in a conduit underground to a box  where a hot tub used to be. Would it be easier to extend that line 90 ft to my music room  under ground and then up through the stucco and dry  wall?
 I just got quoted $5500 for the job the other way, which seemed very high to me. The roof was his idea.
I though I could get some ideas from someone here before I get more estimates
thanks