So, whether you like mashups or hate them I do think they can be original and fun. Case in point: Modest Mouse vs. Ratatat. Charming. The entire Modest Rat corpus can be found here. Scroll down to the Jan 24th entry for a link to the zip file with all the MP3s. Nothing like artists giving away music.
Whether mashing up pop (rap) acapellas and instrumentals a la Girl Talk is something that requires talent or is musically good or not I'll leave to others to debate. I thoroughly enjoy Girl Talk.
I will say that I wish there were acapellas and instrumentals for the more indie stuff I listen to. It's kind of sad, I'd love to sample Marvin Gaye's Trouble Man...but there's not an acapella of it anywhere. There are other Marvin Gaye songs...but my mind tends towards mashing up stuff that doesn't have acapellas. And DIY acapellas never do sound quite right. Maybe someone will eventually make software that can extract vocals properly...I'm not holding my breath.
Off to class for now, I've got a Computer Science midterm at 5, a Professional Practices & Ethics midterm due Saturday and then CS Project 1 due Tuesday. Those 2 CS assignments (midterm + project) make up 45% of my Data Structures grade. Good times. Back later. Probably will finally touch up and post something I wrote about Dad.