Error "Can't make every file of ... into type alias list" - please help!

Question

Hi
I am trying to adapt a script that uses Max (an audio conversion tool) to convert files in a folder to another format. The original script which I found on a forum asked the user to choose the folder with the files in which need to be converted, but I want to specify the folder in the script so that it can be automated. So I changed the line:
set sourceFolder to choose folder
to
set sourceFolder to "Macintosh HD:Users:nick:Desktop:test:"
However I then get the error (this is the only line in the script I changed and the original script works fine):
error "Can’t make every file of "Macintosh HD:Users:nick:Desktop:test:" whose name extension = "m4a" into type alias list." number -1700 from every file of "Macintosh HD:Users:nick:Desktop:test:" whose name extension = "m4a" to «class alst»
Could someone let me know why I am getting this error and how I can sort it. The full script is below.
Thanks
Nick
tell application "Max" to activate
tell application "Finder"
set sourceFolder to "Macintosh HD:Users:nick:Desktop:test:"
set theFiles to (every file of sourceFolder) as alias list
repeat with aFile in theFiles
tell application "Max"
convert aFile
end tell
delay 1
tell application "System Events"
tell process "Max"
click button "Convert" of tool bar of window "File Conversion"
set encoderOpen to true
repeat while encoderOpen is true
try
window "Encoder"
on error
set encoderOpen to false
end try
end repeat
end tell
end tell
end repeat
end tell

Answer 1

nick_harambee wrote:
set sourceFolder to "Macintosh HD:Users:nick:Desktop:test:"
This saves a string (Macin...) under the variable sourceFolder. You then try and use sourceFolder as an alias which doesn't work. To fix the situation try saving sourceFolder as an actual alias in itself. For example...
set sourceFolder to folder "Macintosh HD:Users:nick:Desktop:test:"
or perhaps
set sourceFolder to "Macintosh HD:Users:nick:Desktop:test:" as alias
Either of those should correct your problem.
When using "(choose folder)" you get an alias returned which is why the original script worked fine.