Real bass trombones

[boneagain]

Over a month in the making.... new and improved spectrograms for Mr. Kraft!!!

The player should normalize the volume, not the software. The volume changes the sound spectrum, and merely reducing the volume with the software will only compress the graph. Ideally you would be able to play a note many times, making sure they are all the same volume, and generate a graph that averages them all together. Then when you compare two graphs, you will have eliminated the random variations.

Just learned that the hard way

Having a tuning meter right there eliminates one variable.
I think I have a solid sound level meter around somewhere. I'd use the computer screen, but it gets in the way of being able to hold the horn and watch the tuner (and listen to the simultaneous drone.)

MUCH better results using unequal volume "raw" stuff than computer normalized, EXACTLY as you point out.

Expecting even better results after having the speedo and tach, er, tuner and volume.

Interestingly, the tips of the FFT spikes seem to stablize across volumes for a given position, with the valleys between those peaks going up and down with volume. Obviously, more experimenting required...

See notes these six charts.
Another chart follows the notes.

FFT_Overlays.png

As Brad pointed out, matching volume is crucial. Just to be on the safe side, I matched volume AND pitch as closely as I can these days. I picked A220 in three slide/valve combinations, adding LOTS of tubing into the mix.

Let's start with the SECOND row of plots. I kept the slide in the same position while playin three different dynamics. Lots of visible chart color overlay for each position. Not surprising. We EXPECT timbre to change with volume. Notice that, at least with MY microphone, things taper off a LOT by around 7k Hz.

This row fully supports what Brad wrote about THE PLAYER needing to keep volume consistent.

Which leads us to the first row. Now I do my best to keep my VOLUME consistent, and play the note at the same volume in each of three valve/slide combinations.

This first row is not NEARLY as colorful as the second. Most of the color appears between 5k Hz and 8k Hz. I found it interesting but not surprising that I saw the fewest color differences at the highest volume and most at the lowest.

Now some of you might be saying, "But wait... you are showing content at ZERO Hz!"
Yes, but not as much as you might think. The X axis is logarithmic. and the first peak at 220 Hz is compressed with all the other low octave stuff.

Others might be saying, "But wait... the differences arond 6k Hz are lower than the stuff around 0."
At which point we'd need to remember the "Fletcher-Munson" curve (and updates to it since its introduction in the 1930's.)

from wikipedia:

If we can perceive things around 6k Hz as the same volume as something around 20 dB louder at 200 Hz then things shift a bit.

In fact, looking at the loudness curve we can see that the biggest differences in timbre that we get by adding tubing for the same note occur in the MOST sensitive range of normal human hearing. Heck I can even hear that range at MY age

Why do these differences show up this way? I'm leaning toward reinforcement of harmonics, especially at lower volumes. I think at a piano the way the overtone series of the tubing do, or do not, support the harmonics over the note being played are more visible. I think at louder volumes the harmonic content of the played note over-ride the tube-length factors.

I like the upper right chart best. The blue "p2" trace has the most support in the 6k Hz harmonics. The double-trigger odd-fifth position has the least support.

If my "real" bass trombone only had a slide (no valves) and was tuned so I only had the option of playing THIS note with THIS much tubing, I would have a pretty limited timbre palette at lower volumes.

One could do similar comparisons with other factors affecting timbral differences between "real" and 20th century bass trombones, like bore size or German vs. sackbut vs. other bell flares.

If someone is interested in doing that, send me a PM and we can discuss how to get you the Python code I used to make the charts above.

TECH NOTE: the actual charts are MUCH more fun than what I'm posting here. If you run the code you can zoom in on ANY part of ANY of the charts. You might even be able to add in code to show approximate loudness curve effects.

[jtbandmusic]

'Spose you took a peashooter trigger horn with a trigger... maybe a Olds Superstar or the small trigger Yamaha... and taped the trigger permanently pulled. Wouldn't you have the (kinda) smaller bore, (kinda) smaller bell, and the same length of cylindrical tubing (for all notes in positions 1 through 5)? Take playing a bass trombone part with such a horn. Seems a good way to simulate a long F bass.

John Thompson

[BGuttman]

'Spose you took a peashooter trigger horn with a trigger... maybe a Olds Superstar or the small trigger Yamaha... and taped the trigger permanently pulled. Wouldn't you have the (kinda) smaller bore, (kinda) smaller bell, and the same length of cylindrical tubing (for all notes in positions 1 through 5)? Take playing a bass trombone part with such a horn. Seems a good way to simulate a long F bass.

John Thompson

Partially. There is actually a G-Bass with a sub-0.500" bore, so that bore size is not particularly out of bounds..

But a true F-bass has a 7 position slide with a handle to reach the outer positions. A Bb trombone slide will only give 5 or perhaps 6 positions in F. This leaves a larger than expected gap between the last "regular" (2nd partial) and pedal (1st partial) notes.
'

[boneagain]

Also, by having the extra length in the valve section you will change the color in ways that can be made visible with exercises like the above.

All the bits, like bore size of the valve section, place in the air column where the unavoidable slide discontinuities occur, etc., contribute to what Max states about audible difference between a "long bass" and one making a note by adding cylindrical tubing and leaving the slide short.

[timothy42b]

Also, by having the extra length in the valve section you will change the color in ways that can be made visible with exercises like the above.

All the bits, like bore size of the valve section, place in the air column where the unavoidable slide discontinuities occur, etc., contribute to what Max states about audible difference between a "long bass" and one making a note by adding cylindrical tubing and leaving the slide short.

Somehow I missed this thread. But various persons have said what I would have.

To chime in (sorry) on Dave's thread though, the discontinuities matter and you have to stabilize both pitch and volume.

As I understand it, the harmonics for a given note are fixed by the physics, as is shown by the spectrograms provided. The set of partials are semi-fixed by the length of tubing, but they don't line up as neatly as the harmonics do, because of the discontinuities. What I think that means is that by playing above or below pitch center for a given length of tubing, the upper harmonics (which are fixed) are reinforced differently and the timbre can be colored. Maybe that's the only way timbre is colored if you don't increase the volume to raise the upper harmonics.