[RajatPawar]

pawn Код:

CMD:radioincar(playerid)
{
    if(!IsPlayerInAnyVehicle(playerid)) return SendClientMessage(playerid, -1, "You are not in a car."); 
    else if(IsPlayerInAnyVehicle(playerid)) return PlayAudioStreamForPlayer(playerid, "Songhere");
    return 1;
}

Something like this?