well i do not know if this works on vice city stories but on liberty city stories there was a rockstar loader, heres from wikipedia:
Custom Soundtracks
Rockstar Custom Tracks
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Rockstar Custom Tracks
A special feature (only in the PSP version of the game) is the ability to listen to custom soundtracks.[7] Previously, only Grand Theft Auto games on the Xbox and PC were able to implement custom soundtracks. When Liberty City Stories was released, the custom soundtracks option was featured in the "Audio" section of the menu (by pressing Start in gameplay) but did not have any use. Many people posted on various internet forums asking how to use the feature. At one time, it was thought that these custom soundtrack abilities had to be unlocked, but this would have been very unusual since previous games didn't do this.
A few days after release of the game, Rockstar placed the application called "Rockstar Custom Tracks v1.0" on the official site under the "Downloads" section. This then gave people the chance to use the custom soundtracks feature. The application appears to be based on Exact Audio Copy.
In the application, songs from a CD are ripped, compressed, and converted to files that can be read by the game. Rockstar Custom Tracks (RCT) only allows the ripping of songs that are from a store-bought CD. This was met with much criticism among the fan community. However, fans have found a way to compress and convert MP3 files that are not burned onto CDs[1]. RCT can also look up and use the names from the FreeDB server if there are no names for the song(s). There must be at least one save file in order for RCT to work. It is thought that this will be used for other games Rockstar will release on the PSP from the name. More details can be found in the PDF in the file downloaded from the official site.
naw actually was being sarcastic but I did google it yesterday and everything refers to LCS. I know theres a way, they wouldnt leave that feature out after having it in LCS. Im thinking its either the same instructions as LCS and they share the same folder or its a different folder name... im betting on same folder name that way you have the same songs for both games... gee who'd ah thunk. Ill give it a try later and repost if it works... busy trying to find info on making homebrews.