Can you actually do that? Up-convert from a lossy source so that the file reads that it's 320kbps or whatever, but sounds like its coming out of an old telephone?
A single generation from 128 to 320 wouldn't be too terrible, mind - it'd probably be noticeable to most people on half-decent speakers, but it wouldn't totally wreck the music. A second generation from that lossy-sourced 320 would probably start to get pretty grating, though.
If you're thinking of doing it for artistic reasons, though, I'd say you're more likely to get better results from a judicious selection of high- and low-pass filters, with a flanger or two thrown in.
Just to expand on what eponeponepon said, digital generation loss (by transcoding/compression) sounds quite a bit different than analog generation loss.
A single generation from 128 to 320 wouldn't be too terrible, mind - it'd probably be noticeable to most people on half-decent speakers, but it wouldn't totally wreck the music. A second generation from that lossy-sourced 320 would probably start to get pretty grating, though.
If you're thinking of doing it for artistic reasons, though, I'd say you're more likely to get better results from a judicious selection of high- and low-pass filters, with a flanger or two thrown in.