Here is an awesome video from James Conway, showing a benefit of tongue-blocking I’ve really been enjoying and that’s utilizing splits to play melody’s with a drone note (the drone alternates blow and drawing on 3 and -2.)
I mention splits and flutters which are techniques he’s using in the first half of this video in this post:
So the drone is you can play from -3 all the way up (depending on your mouth size limits the upper end) and have the drone all the while happening on the -2 alternating with 3.
I
-
In 2nd position that is the root, as James is doing in the video.
-
In 1st position it’s the 5th.
Those are both 
excellent notes for drones, so either perspective is fun, and this is a lot of fun on alternate tuned harps (I especially love doing it on Harmonic Minor harps.)
Anyways the FUN WOLRD OF DRONING starts with double stops
-23
34
And then goes to Split-3’s (tip of tongue covers only 1 hole)
-24
35
And then goes to Split-4’s (tongue blocks 2 holes)
-25
36
And then goes to as Split-5 then Split-6 (tongue blocks 3 holes, then 4 holes)
-26
-27 (NOTE: hole 7 is where draw/blow reverses which pitch higher)
Then again a Split-5 then to a Split-7! (tongue blocks 3 holes, then 5 holes)
37
-28
And then the top for me right now is a Split-6 (tongue blocks 4 holes)
38
I can’t do a split-8 (many people can, I heard that George Harmonica Smith could do Split-9’s!?!?)
I Split-5 used to be my widest but as I explored it more I realized the secret to getting wider splits is pushing the harmonica deeper into your mouth.
So coming back down is
38 -28 37 -27 -26 36 -25 35 -24 34 -23
And if you’re getting really deep into this stuff, I have found I can bend -3" while playing -1 regular
For the root I like playing -12 (To imply a I chord, vi chord, or Vsus chord underneath)
Or to play a 13 (To imply a IV chord)
Like a cheesy commercial…BUT WAIT! That’s not all… In case you didn’t watch the rest of this video: then at 1:45, he goes into a killer Irish jig while accompanying himself on the bodhran drum!! 
If you’re wanting to play these kinds of 1st position Irish tunes, Brendan Power has an awesome book and recording of a ton of Irish tunes which I own…somewhere…(if only I could find it!) 
https://www.brendan-power.com/play-irish-music-blues.html
Hope you enjoy this amazing performance from James Conway!
