SUBSTRING in query

This is a query-of-query in ColdFusion and MSAccess
This works ok
<cfquery name="session.getAlpha" dbtype="query">
select distinct signerName
from session.getSigs
</cfquery>
Instead, I would like to select just the "first letter" of signerName in alphabetical order:
<cfquery name="session.getAlpha" dbtype="query">
select distinct substring(signerName,1,1) as alpha
from session.getSigs
orderby alpha
</cfquery>
and it fails. This is giving me a rough time, im just not making the query right ...
Any help much appreciated!