Bradley Lehman video: “Harpsichord tuning: building a scale by ear”

Traio a este blog, por segunda vez esta semana, un vídeo do doutor Bradley Lehman. Se antonte falaba so de afinación, Bradley Lehman video: “Tuning a harpsichord in Bach’s temperament”, no vídeo de hoxe tampouco toca obra ningunha. Segue coas súas instruccións para afinar ou temperar un cravo:

Copio e pego a presentación que aparece no canal en YouTube de Bradley Lehman para este vídeo (hai máis información sobre os distintos sistemas de temperamento na súa páxina “Practical instructions for tuning by ear”):

Tuning a harpsichord from the reference of a single starting note.

In this demonstration we start from an A, and then we derive all the notes of a pentatonic scale from it: F, G, A, C, and D.

The title of this demonstration could also be: “Starting any meantone temperament accurately, by ear.” The notes and intervals are adjusted carefully until they are deliberately impure by the right amounts relative to one another.

*** A transcript of the captions is available here: http://www-personal.umich.edu/~bpl/tetrasect.htm ***

Despite some perhaps arcane terminology, this is merely a simple listening skill of controlling the relative pitches carefully. With practice, and knowing what to listen for, this skill can be developed by any reasonably musical teenager working hands-on at a harpsichord.

The basic technique here is to set up four consecutive 5ths (such as F-C-G-D-A) with exactly the same amount of tempering (impurity) in each interval, deliberately. The 5ths all have to be made slightly narrow, or else we would end up with a major 3rd that is unpleasantly wide and ugly. Tempering is always a series of trade-offs.

In this demonstration a size of major 3rd is chosen first, as boundary, and then the intervening 5ths/4ths are fit equally into that confined space. Here we have chosen to start with a pure major 3rd, for simplicity, but the technique works similarly with any other reasonable size. We could have used a slightly wider major 3rd tastefully, according to the milieu and the keys of the music we plan to play.

The resulting layout is called “meantone” because the whole step (the tone) makes an equal and average size within a given size of major 3rd. That is, for example, F to G being the same size step as G to A, within the major third F-A as illustrated here. The G’s frequency is at the geometric mean between the other two frequencies.

This hands-on tuning method at the harpsichord is entirely geometric/analog, not involving any calculations or any technology invented later than 1600. (Well, OK, the tuning fork was 1711, but it’s not necessary even to have a tuning fork; just some suitable way to assign a resonable pitch to the first note.)

This is the basis for most of the historical keyboard temperaments used on harpsichords, clavichords, organs, and pianos: at least among the natural notes (white keys on a piano), having all or most of them equally spaced in a “meantone” relationship.

After watching the video several times, taking notes if necessary, it might be useful to go through it again only listening closely to the sound (i.e. not looking at the picture or the captions). It might be easier to comprehend in that way, since the technique being taught is a listening skill…not a reading skill.

Of course, nothing substitutes for trying it out oneself at a harpsichord, to get a feel for the types of adjustments necessary.

With enough practice, and using temperaments that are built like this, the whole harpsichord can be tuned accurately by ear in about 7 to 20 minutes.

This same triplets-to-duplets listening skill is also useful in checking the purity of octaves, especially when working on the treble notes. I use it all the time to make sure my 5ths and 4ths aren’t getting too gamey, or conversely too nearly pure where they’re not supposed to be!

Dr Bradley Lehman
http://www.larips.com
Tuning resources and CDs