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Tunable Drum

From bowiki

Drums are generally regarded as having no specific pitch therefore Drum 'tuning' technically is an acknowledged misnomer. The correct term is the adjustment of skin tension.

A 'tunable' drum will have a mechanism to allow either the skin to be pull over a fixed edge or an edge is pushed into a fixed skin. These are known unsurprisingly as the Push and pull methods. The push method using an internal tuning ring is by far the most common.

A third but less common type is to use an internal mechanism within the drum shell to push the top of the shell forward.

The following is a tutorial for drum tuning on a tunable drum that has individual tensioning capability at multiple points on the skin


Tuning a Tunable drum

A 'tunable' instrument will have some form of integral mechanical device designed to allow for adjustment of the tension on the skin. There are many methods and variations available from different drum makers however the basic principles remain the same.

Most common are drums using an internal tuning ring, adjusted by advancing or retarding a bolt (shown). Until the early mid 2000s the most common form of tuning mechanism required a tool. Since then Finger tuning is more common on good quality drums.

Both work by pushing an internal ring up against the skin. The further the ring is advanced, the more tension is placed on the skin and the tone raises in pitch. Some versions have tuning rings built into them, another where the shell is split into two parts. Other forms include external hardware where the skin is pulled downwards.

The net effect of all tuning methods is to move either the shell or the skin in relation to the other and thereby to control the tension on the head.

To tune a drum head from scratch.

Take one bodhrán....

Seat the head

When there is no tension in the drum you need to ensure that the skin is centred and not stuck on the edge where it crosses the shell. To seat it, I simply pless my palm in the centre of the drum and at all the tuning points. This ensures that all sits loosely.

Mechanical Basecamp

The mechanical basecamp is a wee name I give to the positioning of the hardware prior to adjustment. In the case of the bodhrán this only requires youto hand tighten the screws so that they are just touching the tuning ring but are not yet applying pressure.

Order of tension.

To place tension evenly on the drum you need to be orderly in the amounts of tension applied and where it is applied. The majority of good quality tunable bodhráns will have 6 or 8 tuning lugs. In this case you will find it useful to consider them in terms of pairs that sit opposite each other. Occasionally bodhráns will be made with 5 tuning lugs, these are star tuning systems and pairs don't apply. Lugs should be numbered 1 - 5 (anti)clockwise around the drum

With pairs you will need to identify one pair as pair one, it is immaterial which you select but you will need to remember it for the tuning session. If you position pair one as being at 12 O'clock and 6 O'clock then you will have other pairs spaced evenly to the right and left.

pitchedpairs.jpg eightlug.jpg

  • In a 6 lug drum you will have a pair (Pair 2) at 2 & 8 O'clock and another (pair 3) at 4 & 10 O'clock.
    • The 6 lug drum would be tensioned 12, 6, 2, 8, 4, 10 or a variation thereof - Repeat
  • In an 8 lug drum you will have a pair at 3 & 9 O'clock (Pair 2) , 1.30 & 7.30 (Pair 3) and 4.30 & 10.30 (Pair 4)
    • The 8 lug drum would be tensioned in the following order 12, 6 then 3, 9 then 1.30, 7.30 then 4.30, 10 30, variations are possible of course - Repeat as necessary
  • A 5 Star system drum will be tensioned in the following order 1, 4, 2, 5 ,3.

The idea behind the tuning is to work around the drum adding tension bit by bit as evenly as possible so that you finish up with each lug applying identical tension.

Applying tension

Starting with Pair 1, grip the 12 O'clock lug loosely and hand tighten until it resists and your fingers slip, do the same on the 6 O'clock lug with the same amount of grip, follow the pattern above for your number of tuning points. When you have done this, check if you have a note. If not then repeat with a little more grip tension. If the lugs are stiff then you may use whatever tuning tool is appropriate but move in terms of 1/16 or 1/8 turns and ensure that you are consistent as you move through the pattern

Once you have a note, you need to check that it is the same at each tuning point. To do this tap about an inch into the skin directly above the lug. Compare this with its neighbours and those opposite. Hum each note that is produced and compare to see if there are any differences. You will need to adjust the lower pitched lugs to match the higher pitched one.

If there is a significant difference then I suggest you re-tune from scratch again rather than waste ages balancing an already unbalanced drum head.

When you are tuning up the lower pitched lugs you will also be raising the overall tension of the drum so the lug with the note that you are trying to achieve will also be going up but by a smaller amount. Because of this it may take a number of progressively finer adjustments to achieve a single note.

The tension placed on a drum goes on in a fan-like manner, if you can imagine tugging on an edge of a flattened bedsheet you can imagine the tension pattern. The greatest tension effect is diagonally across the drum and this is what gives it the paired tone quality. You may have to fractionally adjust other lugs to compensate.

Tips:

  • A tone is mirrored at the opposite lug of any diagonal pair.
  • Adjustments should be split 50/50 between paired lugs as far as possible
  • You should try to adjust tuning by raising tension not lowering it.
    • Lowering tension relies on the skin retreating smoothly back over the bearing edge which is not guaranteed. If you do need to lower tension, you must back the lug off substantially and then tune up to the desired pitch (not recommended as it unsettles the overall tuning)

When you have ensured that there is a single note at all the lugs then you will have successfully tuned the drum to its lowest tuning point. This is tuning basecamp, from here you need to choose the overall tonality of your drum based on the sound you wish to achieve and then to fine tune to that point.

Overall tonality & pitch

To raise the pitch of the drum from here, you only need to evenly apply increasing amounts of pressure to the head. At this stage, 1/4 turn of each lug is a huge amount so I'd recommend working in 8ths or 16ths. As you finish each round of the pattern, check the accuracy of the tuning at each lug and adjust as appropriate. Continue this process until you find the tuning region of the drum that you are looking for or that you find pleasing.

Fine tuning

Ok so this is the nitty gritty. I assume that you have achieved a successful overall sound, the same tone at each lug and a pitch that's good for you. if you want your drum to deliver a full pure tone, you need to extend the above process to micro levels. Here's how you do it.

As you tap the drum skin at each lug you will hear one main tone but you will also hear smaller tones that form a component part of that main tone. you may also note that there is a wavy, phasing kind of sound usually higher in pitch. These sounds are known as a beat frequencies. As you tap at each lug you will notice that these beat frequencies can vary quite widely and again the pairs effect will apply These harmonic overtones and the beat frequencies they provide are your friends.

Tip:

  • Listen closely to the sound of your drum, can you hear that the overall sound is made up of several sounds?
  • Ensure that what you are listening to & adjusting is the correct thing, it is normally fairly obvious but it can be deceptive and may take a few tuning sessions to develop the ear to be able to pinpoint overtones accurately.

Work your way around the drum and identify the pair with the fastest vibrating beat frequencies. Adjust one of the lugs by a tiny amount and listen to what happens to the beat. Does it speed up or slow down? if it speeds up then you're going the wrong way, if it slows down then you are moving in the right direction. Adjust that lug and it's opposite partner so that you get it to its slowest beat. (it's ok to tune down using these small adjustments). Check again that the overall tonality of the drum is where you want it.

Go around the drum again identify the next fastest beats and adjust those accordingly. Work your way around the drum as many times as it takes each time adjusting until you get the beat frequencies to their slowest. Your aim is to achieve zero beat frequencies so that these overtones become a single pure tone. I often find that there is one final lug adjustment that just causes the whole drum to drop into tune, it can be quite amazing.

When you have achieved this then your drum is perfectly in tune with itself, a perfectly efficient tuned instrument.

Help! I can't get the beats to stop

There may be instruments where no matter what you do you don't seem to be able to get the beat freqs to stop. There are a number of potential reasons for this

  • The bearing edge (where the skin leaves the drum) is damaged
  • The drum isn't round
  • The drumshell is twisted (torsion)
  • The skin is uneven in its thickness
  • One of the pairs or lugs is drastically out of tune but is being masked by others taking the tension
  • The drum is unbalanced
  • You haven't been working with the correct sounds

Yes I know I'm a nerd

Ok so not everyone is going to go to this trouble every time they play their drum, I don't! although I do ensure that I have the gross tuning to a consistent note. The value in doing this is that now you know how your drum works and how the adjustments affect the sound. The act of undertaking micro tuning is an intimate act and can only improve your relationship with your drum and your understanding of what's going on. That's never a bad thing, is it?

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