how to run shell commands in applescript

Says here in the title you want to do it using shell commands, but have you tried something like this, which is AppleScript?

tell application "Finder"
    set h to home as alias
    set mn to the name of every file of folder (h & "Dropbox:Audio:Features:SAL350 Ruiz, Luis NPR:Audio:" as string) whose name contains "main"
    return mn
end tell

If you are looking for your search results as UNIX pathnames, try this form.

tell application "Finder"
    set h to home as alias
end tell

do shell script ("find " & POSIX path of (alias (h & "Dropbox:Audio:Features:SAL350 Ruiz, Luis NPR:Audio:" as string)) & " -name \"*main*\"" as string)

Does that help?