Note - before I start this post, let it be known that I am assuming you are a right handed banjo player; if you prefer your 5th string peg on the other side of the neck (as my own mother would, were she a banjophile), please swap "left" for "right" and vice-versa in the remainder of this post.
The right hand of clawhammer banjo players gets a lot of attention; this is arguably deserved since the "down-picking/rapping/knocking" motion of the right hand separates this manner of banjo playing from the way that most other plucked stringed instruments are played. Also, the percussive techniques we employ with our right hands (e.g. slow brushes, clucks, galax licks, drop-thumb-slaps) are the real head-turners in jams and are probably key to a lot of stylistic differences between players. While the left hand is the unsung hero of the Clawhammer story, I would argue that putting even a little bit of thought into proper left hand position can hugely benefit your playing.
In spite of all this - the left hand is pretty much ignored in most clawhammer banjo teaching material. I'll admit that I haven't done an exhaustive search on this, but in my experience the author of a tab rarely indicates which finger to use when fretting a note, and I've talked with many new players that find this to be a bit of an oversight. When left to fend for themselves, many people simply gravitate towards using the index and middle (i.e. the "strong" fingers) for as much left hand fretting as possible, occasionally employing their ring finger, and virtually never using their pinky. While you can go far with this technique in Old Time music, these players end up moving their left hand way more than necessary (which can impose a speed limit to one's playing), and having to use slides rather than choosing to use slides in many places.
So what's the solution here? For this I look back to my years of squeaking around on a Cello in Middle- and High-school (believe me, I was never very good...): hand positions are my way of navigating the ever-present "which finger to use for which fret" conundrum. Before going any further I'll give a video example from my side-gig as a "professional banjo tester" at elderly instruments. Here's me playing Hobart Smith's "Banging Breakdown" (sans the eponymous "banging" which always sounds sloppy in my hands) on a Deering Goodtime Americana:
full video link: https://www.youtube.com/watch?v=Veb70cJ-eo4
Nice shirt, huh?
I play "Banging Breakdown" in a tuning pretty close to what Hobart used (I use gCGBD; I think Hobart used gCGBE) and the fretted notes all fall on frets 1-4. Since I have 4 fingers on my left hand, I can assign each finger to a fret and play the whole tune without shifting my hand up or down the neck. This does require me to use my pinky, quite a lot actually! But, this is a good thing, and only gets better with practice.
Summarized Hand position guide for Banging Breakdown:
any time I press down the 1st fret I use my index finger
any time I press down the 2nd fret I use my middle finger
any time I press down the 3rd fret I use my ring finger
any time I press down the 4th fret I use my pinky finger
Seems obvious right? Lets go to the next level - many tunes require you to shift hand positions (basically you can't cover everything you need to do with a single one). Check out my version of "Brushy Fork of John's Creek," an Art Stamper tune that had a bit of a popularity surge in VA a couple years back, Played on a 12" Pisgah Possum:
full video link: https://www.youtube.com/watch?v=ovjxcOZZFb4
Different day, different banjo, same shirt : )
I use 2 left hand positions for this tune: I start in this position (which I'll call hand position A):
Hand position A (for Brushy fork of John's creek):
any time I press down the 3rd fret I use my index finger
any time I press down the 5th fret I use my middle finger
any time I press down the 6th fret I use my ring finger
any time I press down the 7th fret I use my pinky finger
A couple of notes on hand position A:
1) Yes I do skip fret 4 on purpose (and it doesn't come up in this tune); this is common in cello hand positions (do a google image search on "half position" for cello) and you can typically skip a fret between your index and middle without much discomfort.
2) Where my ring finger would go is somewhat hypothetical since I don't actually use the 6th fret in this tune either.
I have to reach for the 2nd fret of the 3rd string twice in the A part - this is not covered in the above hand position so I move back to hand position B (below); in theory you could simply think of as "breaking hand position" to get a hard-to-reach note, but any time I slide my thumb on the back of the neck, I think of it as changing positions. Furthermore, I end up using hand position B for the whole B part as well.
Hand position B (for Brushy fork of John's creek):
any time I press down the 2nd fret I use my index finger
any time I press down the 3rd fret I use my middle finger
any time I press down the 4th fret I use my ring finger
any time I press down the 5th fret I use my pinky finger
So, take a second to watch the above video again and note the hand position switches. One more example, is "Fine Times at Our House" a Hammonds family tune from WV that makes it way pretty far up the neck. You can see me playing a full A part here (then the video gets overdubbed with my "sales pitch" about the OME Northstar, which really is a nice banjo btw!)
full video link: https://www.youtube.com/watch?v=052xPB-Dm5Q
Whats with the new shirt? I kinda liked the old one better...
So this tune actually uses 3 hand positions (all of which you can see in the A part). I won't give describe them as thoroughly as before, since you likely get the point by now:
- The 1st position I use covers frets 1-4 using index-pinky fingers without skipping any frets (same position I described for banging breakdown above)
- The 2nd position I use covers frets 2-5 using index-pinky fingers without skipping any frets (same as "position B" for "Brushy Fork of John's Creek")
- The 3rd position I use covers frets 5-9 using index-pinky fingers, and skipping fret 6 (similar to "position A" for "Brushy Fork of John's Creek" but moved up 2 frets).
Watch the video again and see if you can ID when I use each position, and more-importantly, when I switch.
I'll leave you with one final example on how to put slides back into your playing with hand positions - basically my rule is to "slide in" to the desired hand position rather than "sliding out" of it and having to move back to the position you'd like to be in. Here's an example of what I'm talking about using "Johnny Don't Get Drunk" on a fretless 12" Enoch Tradesman:
full video link: https://www.youtube.com/watch?v=WTEEv8dNJwo
...wait, where did the beard go?
I'm not sure what the point of playing a fretless banjo would be without using slides and when I get one in my hands, I really can't help but put a few into whatever tune I'm playing!
Though its a little harder to tell without frets for reference, I am staying in one hand position for this entire tune (the same position as "Hand position B" for "Brushy fork..." above). But several times in both the A and B parts, I slide "into" this hand position, starting ~1 "fret" back; in every case, I am sliding from the imaginary 3rd to 4th frets, with my ring finger (which ends right where its supposed to be, on the 4th imaginary fret, in this hand position). You could make the same sound by starting in the correct position and sliding from imaginary frets 3 to 4 with your middle finger, but then you'd have to move back down to get to your original hand position - I'm a lazy banjo player at heart and 2 moves are not better than 1 in my opinion : )
Final thoughts - This method of playing isn't for everybody, but whether you end up using hand positions or not, I hope you got something out of reading this. I should also say that this approach doesn't work well for every tune I play - particularly those with a lot of chords (especially C/D-shape chords in open G/A tuning, which require you to put 2 fingers down on the same fret). However, I don't think I could keep track of how to play super-notey tunes like "Fine Times..." without using hand positions as an organizing principle.