Some years ago, while studying the technique of the wonderful Gwen Foster (of the 'Carolina Tarheels') I discovered that one of his many techniques included one identical to that used to obtain what I would call a 'harmonic warble' when whistling. (For an excellent description of this effect, read the first few pages of Mark Twain's novel 'Tom Sawyer') The result is exactly the same:when playing a blow-bend, the tone oscillates between the two extremes rather than sliding up and/or down. Foster uses this, a rapidly alternating toungue-block, and a gurgle (on the draw) to sustain an ornamental effect that sounds like a mallet instrument, keyboard or cross-picking on a string instrument. He also uses the whistle/tongue flutter on a draw six bend, I think, although, depending on the pitch of the harp, this can be achieved by the epiglotus alone.
However, I thus formulated the opinion that Foster was probably a hell of a whistler, and, on a trip to the Nashvile Country Music Hall of Fame archive in 1980, I expressed just this opinion to British music-historian, Tony Russell. Tony, barely hesitating, withdrew from the archives collection a 78RPM disc of 'The Foster Twins'-namely Gwen and Garley Foster, both of whom played in the Carolina Tarheels and whose styles were somewhat similar in a few areas. (The two Fosters are said to be un-related, something which I find hard to accept) All this I alredy knew as fact. However, to my amazement, my hypothesis was proven correct immediately. The track Russell played to me was called 'I Want My Black Baby Back', and featured these two fine harp players singing and whistling, using this same tongue-flutter technique that had led me to my hypothesis. Garley Foster, incidentally, on account of his whistling prowess, was billed professionally as 'TheHuman Bird'. (Incidentally, the technique is simply to repeat the letter 'L' while bending, and works best on blow bends)
Obviously there are other precedents for associating whistling and harp-playing. Toots Thieleman is an obvious one. Less obvious is my fellow countryman P.C.(Percy)Spouse, who, in a recording and vaudeville career combined his flawless diatonic playing with whistling novelties, imitations etc.
Lastly, I shall humbly add that I am both a harmonica player and an habitual whistler. I think that any kind of oral or lingual skill can only help your playing.
Cheers, Rick Dempster. Rick Dempster RMIT Libraries E-mail: ric~ib.library.rmit.edu.au