Well, given the following works:

>>> import array
>>> a = array.array('d', [1.2345])
>>> b'' + a
b'\x8d\x97n\x12\x83\xc0\xf3?'

It should also work for bytes.join().
I guess that means I'm against the strict-typedness of memoryviews. As the name suggests, it provides access to some memory area, not some structured array of data.