From my friend who directed the 'traditional' (US) band I used to play in:
"Be aware that concert band music in the US is very different from brass band music in the UK, and they are not compatible. If your friend is in a US amateur band, it's probably a mixture of woodwinds, brass, and percussion in a somewhat flexible format, whereas an amateur band in the UK is most likely and all-brass group with specific instrumentation."

I remember playing some folksong-based pieces in his band, and I've asked him to suggest specific pieces which might be available from Chatfield Library; he said he'd get back to me later this week.