Find the longest musical substring
Pyth, 25 23 bytes

pdJef!-T&lt;G7+k.:@Grz0)lJ


2 bytes saved thanks to @Jakube.

Demonstration. Test harness.

Explanation:


rz0: The input, in lowercase.
@Grz0: Strip any non-alphabetic characters.
.:@Grz0): Generate all substrings.
+k.:@Grz0): Add in the empty string.
f ... +k.:@Grz0): Filter over these strings.
-T&lt;G7: Filter each string for non musical characters.
!-T&lt;G7: Negate the result. This is True if and only if the string was musical.
f!-T&lt;G7+k.:@Grz0): Filter out the musical strings.
ef!-T&lt;G7+k.:@Grz0): Take the last such string. .: orders substrings by size, so this is also the longest musical substring.
Jef!-T&lt;G7+k.:@Grz0): Assign the result to J.
pdJ: Print J, with d, space, as the ending character.
lJ: Then, print the length of J.