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Art of Glass

If you're short of a new source of samples you could do worse than to turn to the glass (not the bottle). Tom McLaughlin explains how a wine glass can provide a wide variety of unusual tone colours.

Looking for an inexpensive way to expand your sample library? Last night's wine glass could become the star of your next composition.

I'VE DONE IT, you've done it, we've all done it at one time or another. Maybe back in physics lessons or trying to occupy your hands while talking (probably incoherently) over a glass of wine. Fact is that rubbing the rim of a glass produces a most pleasant sustained sound - and one that can easily be captured and turned into a musical instrument with a sampler. Rubbed glasses can be used on their own to take the place of haunting bowed strings or voices, and mix well with any number of sampled or synthesised sounds to add a magic, er, glass-like timbre to a composite.

Thin-walled glasses seem to speak more readily than thick ones. Thin, fine crystal gives the sweetest sounds. Be very careful that there isn't a chip out of the rim or you'll put a nice slice in your finger-tip - probably without feeling it until you've got blood in your coffee, in your disk drive, down your 501s...

Getting long smooth notes takes a bit of practice, learning how much pressure is needed to make a glass "sing". To obtain the best results your hands and glasses should be clean and free of any sign of grease or oil. Washing them thoroughly first should do the trick. Keeping a bowl of water handy to dip your fingers in as needed is a less sticky, and more hygienic, way of going about it than licking your fingers every few seconds.

Different pitches can be obtained in two ways: using different sized glasses or filling a glass with water until you reach the desired pitch. For a comprehensive multisample both methods will be of use. Unlike filling bottles up with water when making a set of blown bottle samples, filling a glass up with water will lower the pitch when rubbed. An empty glass will give you the highest note it's capable of producing - don't ask me why; the very first time I experimented with tuning a glass with water, I thought my ears were playing tricks on me. Tuning your glasses will only give you a range of a minor third to a sixth lower than their empty pitch, a major third or fourth being a domestic glass' most musical-sounding range.

Small liquor glasses may be used for the very high notes, wine glasses for mid-high, half-pint glasses for the mid, with pint glasses and brandy snifters for the mid-low and low. Laboratory beakers can be used for a complete set of samples as they're available in sizes ranging from a few millilitres up to several litres, and using the same make of beaker throughout will give you a consistency of tone hard to find with a variety of household glasses.

Do you want a wet set or a dry set of rubbed glass samples? A "wet" set of glasses (using water to adjust the pitch) will have a dreamy pitch and tone colour modulation as the water moves about, but, unless you're doing an underwater scene, filtered "dry" samples (relying on a collection of glasses for different pitches in a multi-sample) mix smoother with strings.

Playing Glasses

RUBBING GLASSES HAS a lot in common with bowed strings - to all intents and purposes your finger is your bow. A legato note requires following the rim of the glass with the flat of a finger in a consistent circular motion. You'll find that you can get about half way around the rim of a glass before you have to change the position of your finger, so each complete revolution will be made up of two distinct cycles.

If you develop a really good technique you might be able to do an entire revolution in one cycle, but either way, unless you loop around a few examples of samples there will be some natural cycles in your loops. It's part of the charm of rubbed glasses, and if you have the help of visual editing it will actually make positioning long loops easier. To save on memory space in a multisample, all the sample data you need is the attack of a note and a loop around the first smooth cycle or two of a note, discarding the remainder.

"Unlike filling bottles up with water when making a set of blown bottle samples, filling a glass up with water will lower the pitch when rubbed."

Once you've got the hang of playing glasses, you'll find that you can elicit staccato notes with a short sharp rub of the glass, and removing your finger carefully once a steady tone has been produced will allow the note to decay naturally. Thin, finer quality glasses will ring clearer and longer than your garden variety pub glass.

You can also pluck a glass with your nail or a soft plectrum, again higher quality glasses have a more musical tone. If plucked forcefully, you'll set any water in the glass into a rocking motion, giving an ethereal, wet vibrato. This is really nice to use in a Loud/Soft keyboard map with a gentle, non-vibrato pluck for the soft, bringing in the brighter, vibrato version as you play harder. Try this as an additional tine element in a layered electric piano sound - it could give the ubiquitous DX7 Rhodes some competition. You can also mix different pizzicato glasses adjusted to the same pitches together for an ensemble pizzicato. A small loop, around one or two wave cycles, enables plucked samples to ring on longer than naturally and makes some fun manipulation with a VCF and VCA possible. And then there's tremulando glasses - rubbing a glass rim rapidly back and forth for a shimmery effect. Eerie.


MIKING SEEMS TO give a sweeter sound if performed around the side of a glass rather than focussing on the rim. Positioning the mic about 10" away should do the trick. Cutting all frequencies below 50Hz or so with an equaliser or filter will minimise room noise and the rumbles of any passing traffic. (You'll hear these more clearly when a sample is transposed higher so play it safe by filtering.) And if you're working with sampling rates lower than 25kHz or so, a bit of top end filtering wouldn't go amiss either.

You might find the added resonance obtained by holding the base of the glass against a wooden surface (such as guitar, piano or table top) with one hand and rubbing with the other attractive. It's rather like using a tuning fork really. If you don't, a towel or pad like those made for computer printers will help cut down on vibrations passing through to the surface the glass is resting on.

A lot of high-frequency harmonics and partials are produced by a singing glass, so you'll need a fairly high sampling rate for your sample to sound natural. For this very reason it's a good idea to divide sampling your rubbed glasses into two sessions. The first one covers recording glass rubs onto analogue or digital tape, the second concerns sampling those recordings. During the second session you can experiment with various equalisations and sampling rates, seeing how far you can go before you get clipping or aliasing of your samples. Rubbed glasses have a somewhat piercing quality that can be sampled as is and "mellowed" afterwards with a filter, or adjusted at source with microphone choice, equalisation, a lower sampling rate or a combination of these.

Of course sampling "silly" things like rubbed glasses tends to be done when you're in "that sort of mood" and have a glass in your hand (or more likely to your lips). But by taking the time to experiment with stretching the possibilities of instruments while still in the pre-sampling recording to tape (and manipulating them by editing), you'll most assuredly reap the benefits of a more interesting set of samples. I've found that if you play a rubbed glass sample back very slowly, stretching out the attack tremendously, you'll get an ambient, slightly metallic, almost ethnic sound. With a percussive envelope fading to nothing before the sample reaches its steady state, you'll find you've a new sound that mixes well with bongos, cuicas, log drums and the like.

"To save on memory' space in a multisample, all the sample data you need is the attack of a note and a loop around the first smooth cycle or two of a note."

A thorough sample recording session would include recording a first pitch dry, and two subsequent pitches wet, legato rub, staccato rub, tremulando rub, pluck, pencil tap and pencil eraser tap for each glass.

You should digitally fade in samples with rough or lengthy entries to polish them up and save on memory space. Be sure to leave at least a little bit of rough edge at the beginning if you want your samples to sound natural. Editing off the appropriate amount at the beginning of your samples will give a more percussive sound which feels really good when played from a keyboard - not quite an electric piano and not quite a bell to uninformed ears.

Most samplers have enough memory to store six or more legato loops at a respectable bandwidth on a single floppy disk. This should be more than enough material to put a multisample together from. When dividing up your memory space, think in terms of sets of sounds as follows.

- Several shortish loops and a long one or two for an Ensemble Map, layered so that you've one long loop under shorter ones.

- Taking advantage of any velocity switching or cross-fading and constructing sets of Dry/Wet, Legato/Staccato, Legato/Tremolo, Tapped/Rubbed glass samples.

- Putting together keyboard split maps with an electric piano-like percussive map on the left three octaves and a legato set on the top two octaves.

Assembling a good collection of glass samples is an effective way of extending a sample library, whether it's for an Akai S612 or a full Synclavier system - and it's unbelievably cheap.

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Dr T's Fingers

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Roland E660

Music Technology - Copyright: Music Maker Publications (UK), Future Publishing.


Music Technology - Oct 1988



Feature by Tom McLaughlin

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