[Konstantinos]

You show the dialog in the loop so it will only show the first song and then you return a value which stops the loop.

pawn Код:

new string[150];
for (new i; i != sizeof (MusicInfo); ++i) format(string, sizeof (string), "%s%i) %s\n", string, i + 1, MusicInfo[i][SongName]);
ShowPlayerDialog(playerid, 7, DIALOG_STYLE_LIST, "Music Player", string, "Play", "Cancel");