Each year, I try to coordinate my learning so that I can make a seudat mitzvah during the nine days and some close friends can have some meat and wine to celebrate. Does the siyum also allow them to listen to music, do laundry etc? What if the live music was part of the siyum (inasmuch as it enhances the simcha of the moment)? Does the siyum change the nature of that entire day for the participants, or just the time at the siyum? Does it make the time at the siyum as if it is not in the nine days, or just allow a particular type of behavior on top of the other issurim of the day?
The Rama writes meat and wine by a seudas mitzvah davka and the food can only be eaten in the room of the siyum(Mishna Brurah 551:75).It seems that meat and wine are the only exception and it only applies during the seudah,not the rest of the day.
It should be noted that planning a siyum to davka come out during the nine days is not so pashut,even though there are those who are matir.