an RNC is a very nice, transparent compressor. i've got a love/hate relationship with mine.
are you playing the bandoneon yourself? or are you recording someone else playing? if the latter, any reason you can't just ride the gain along with the dynamics of the song? if the former, and you're recording yourself, maybe instead of compressing, you could move closer and farther from the mic in conjunction with the louds/softs.
most usually, i prefer employing mic and mic preamp technique to compressing. although, i'm certainly not scared to compress to tape when i want to.
cheers,
wade