The Teatro Colon is a most beautful building with great accoustics. It is SOOOOO CHEAP we sat center isle - row 14 for the National Symphony the last week of November and paid $2.60 US each. An other couple purchased 4 box seats for $29.00. Simply go to the theatre, go around the side and turn into the entrance for ticket purchases. Note - when it is time for the performance go around to the back ot the teatro as that is where the entrance is - not on what you think is the main street.
Enjoy - it is worth spending a couple of extra nights in Buenas Aires just to attend a performance. Log on to www.argentina.com
to find a schedule of performances - not it is all in Spanish. Good luck and enjoy.