ABOUT PLAYING THE SAW

Choice of a saw:

I play two musical saws myself:
Sandviken Stradivarius. (Made since maybe 80 years at the saw factory in Bollnäs, is most easily ordered in a hardware store. Nowadays Bahco took over the company, but except for a small change in the logo, the saw is still the same, no. 296 in their catalog.)
Speliplari (made since maybe 30 years, from the Pikaterä saw factory in Kausala, Finland, can be ordered from there).
Stradivarius is in principle the same as an ordinary hand saw of that size, and except for the brand logo on the blade, the difference is only that the teeth aren't inclined and hardened.
Speliplari, designed by the musician Aarto Viljamaa, has no teeth (which explains the name, meaning "play blade"), the handle is made of black plastic (on the model I have) and the steel is a bit thinner and thus more flexible, it's also shorter than the Stradivarius.
The playing character is different: Stradivarius has a deeper, stronger and longer tone but is less flexible than the Speliplari. I also find it easier to have control over the overtones on it. The fundamental note on the Stradivarius has 2 octaves of scope, the Speliplari something similar. For solo playing I prefer the Stradivarius, for fast improvisation with other musicians, I prefer the Speliplari. I often carry both of them in the same case (that I built myself). If I would choose only one, it would be the Stradivarius. I also have the impression that it has the best reputation among other saw players internationally.
There are many other musical saws made, at least in germany and the usa, longer as well as shorter. The prize varies very much.
It's of course possible to play ordinary saws (preferably long hand saws) as well, but be careful of the teeth that can easily hurt you and your trousers.

Treatment of the instrument:

Never use fat and avoid touching the saw blade with your fingers other than on the tip where you bend it when playing. In any case, the back of it (the edge opposite the teeth side) should never be touched but be kept dry.
If it becomes dirty, clean it with alcohol if you can, otherwise it's important to dry it as soon as you can. A rusty saw sounds much worse.
If you haven't used a bow before, the same thing applies there - never touch the horse hair, release the tension of the bow when not using it, and put on rosin before playing.

How to play:

There are many techniques, but this is probably the most common one:
Sit on a chair of normal height, put the handle of the saw between the thighs inside the knees. You souldn't have to squeeze, the saw should be able to rest by itself without being kept by the hands and lean upwards-to the left (i.e. if you want to hold the bow or beater in the right hand, otherwise it's the other way). Try to hold it in a way so that the blade doesn't touch your leg but is free in the air.
Put the left foot outward with the heel in the floor, and the right foot a bit inwards with the heel a bit above the floor. This makes it easier to direct and makes it possible to do vibrato if you have a "nervous shaking” in your right leg. (You can also vary the expression with vibrations of your left arm.)
Take the tip of the blade with a light grip of your left hand. The thumb you put about 10-15 cm (4-6 inches) into the blade, and the other fingers grip the end of the blade. It's enough with a very small tension for the blade to be able to produce a tone (it's actually enough with the weight of the blade itself to get a tone, but it's easier to have control if you hold it with the hand). The thumb with a light pressure down, the other fingers with a light pressure upwards. So no extreme bending. In principle, you should bend the blade into an S-form, where the first bend is very small and the rest of the blade below the hand consists of the other bend.
Hold the saw with a light tension in this way, and now I propose you to start with beating the blade with a mallet. For my part, I use a big bass piano hammer, but you can just as well use a felt mallet for percussion (the saw is classified as a bowed idiophone, but it can also be played as a percussion instrument) or something similar. I know of a saw player that uses the cork of a termos. The hardness decides what kind of timbre you get, try different things.
When you have a tone, bend the left arm slowly up or down and observe one important thing: the tone rises and moves up towards the tip when you bend down the tip of the blade, and the tone sinks and moves down towards the handle when you lift up the tip with the hand. Different notes, thus, come from different locations on the blade. This is especially important to observe when you want to play with a bow.
Use a bow of your choice, it should be well rosined and tensed. I use violin bows myself but anything goes, also home-made ones. The easiest grip on a bow is upside-down compared to how you play the violin. Hold the right hand straight forward, the thumb on the frog (the sliding piece with which you tense the horsehair) and the other fingers around the stick, in such a way that the bow points downwards from the hand. To get a tone, you need to find the right place to play, otherwise it can become completely silent. The easiest way is to strike it with a beater first, and then localize where the tone comes from. Put the bow with a slow and stable movement with just enough and steady pressure on the back of the saw, in 90 degrees (right) angle to the blade on the point where the sound comes from. I think the best effect is reached with a small angle inwards (towards your stomach) when the bow is moved upwards, and a small angle towards the feet when it's moved downwards. Control speed and pressure in order to get the volume you want, you can play from very strong to almost nothing if you do it right. If you want to let the tone sound release by itself you lift out the bow from the contact with the blade, if you want to stop it abruptly, you can stop the bow while in contact with the blade.
Make sure you have a tone and then slowly bend the left arm without contact of the bow so you can hear that the tone moves. Strike another time with the bow on the point where the tone is now. Change the pitch, move the bow, so you learn how to control the instrument. Some say you should play at the peak (the middle) of the bend. Try if this idea makes it easier.

A small saw can (with some difficulty) be held under the chin as a violin.
I've seen some holding the saw with the feet instead of with the thighs.
I often play two saws at once. I usually have the Stradivarius closest to me, and the Speliplari, with the back inwards, closest to the knees (on the picture above it's the opposite). The bow goes between the two and I turn it alternately in order to play either saw. The left hand holds the tips of both saws and it's possible to bend them partly separately from each other. The sound of two saws is the best there is.
You can also play two saws by putting them on top of each other, so the backs are parallel to each other. By combining these techniques you might be able to play four saws at the same time?
The bowing technique has big impact on the sound, by applying extra hard pressure, you can achieve squeeky sounds.
You will soon note that the saw has a number of overtones, that originate on points that are on different locations than where the fundamental (the deepest) is. Most saw players tend to avoid these, but I think they make very interesting effects. Those are between the fundamental and the handle. If you find and hold a stable fundamental note, you can move the bow and play them partly separately from the fundamental, getting several notes at the same time. Note that the pitch difference between those don't correspond at all to the ovetones in a string- or wind instrument. You can get at least 2-4 tones at the same time. You can also get them separately, without the fundamental, and make them slide over and under each other.

The same day, Laif replied:
But it also gives a more “controlled” knee vibrato. The length of the rope/strap is of course very important. But also one-legged people are given a chance...
Above all it's comfortable in long sessions. You can even put the noose all the way to the left foot (the red) if you want. Then, the length of the rope or height of the chair aren't as important.
I saw the light!!
About the Welin story, I've heard it from a local comedian I once shared the stage with. When I brought up the saw, he came back up again and intruded with this story. The ending he probably invented himself...
It would be an honor to be mentioned on your page!
Good you didn't cut my technique short...

Amplification:

A saw has a stronger sound than you might think, but if you must amplify, or record, a saw, it's most practical to place the microphone under and behind the blade, otherwise it's easily in the way of the playing, and from this position, most of the notes are caught. Look out for feedback which easily occurs with this instrument.
Sometimes I've seen, and also tried myself, contact mikes on the blade, but so far I thought this was too problematic with this instrument. The sound is too sharp and uneven for my taste.

Read about my piece for saw ensemble (that you can hear as well).

Other saw playing resources:

Natalia Paruz (The Saw Lady).
The Singing Saw Gazette
Current Guinness world record of the size of a saw ensemble at Gostyn, poland.
Tutorials, listings etc
Savbladet (danish, english)
International Musical Saw Association

Girilal Baars
Pierre Bastien
Catherine Christer Hennix
Paul Lovens
Finn Loxbo
Terje Mentyjærvi
Steve Noble
Hal Rammel
Dorothea Schürch