The dream of a double slide B flat contra bass trombone is to be able to play contra bass trombone using regular slide positions. But the double slide contras have a reputation for being a stuffy and hard to play instrument. Here are some ideas for improving the double slide contra.
The photos show an instrument with the bell of a F contra with the double slide of a BB flat contra. The fit is not perfect but it does fit well enough together to test play. The resultant instrument is in CC. The 1st valve gives a slightly flat BB flat, and the second valve gives a flat CC#. The sound is much better IMHO than with the original BB flat bell section, and it is not as stuffy!
This finding was confirmed by test playing the BB flat bell section with the F contra slide. This combo gives something like d flat, and although is more open than the complete BB flat instrument, is more stuffy than the F bell section. Significantly it does not have a particularly attractive tone, having something of a braying quality. This experiment tells me that at least some of the problems of the BB flat contra are in the bell section.
Back to the Contra with the F bell section and the double BB flat slide. A good usable instrument could easily be made from these parts. It addition to a better sound and less resistance it could be pitches in either CC or BB flat with a G or F attachment. The slide would retain 7 positions on the BB flat side. Played in BB flat, you would use the F valve to low D flat, then use the CC reducing valve for low CC and BB. Played in CC you would use the G slide to play to low EE flat then use the B flat valve to low D and C#.
The following changes would need to be done to the bell section, and if carefully planned the bell could still be used with the F contra slide.
Shorten the D valve tuning slide slightly so it can be used as a BB flat valve.
Shorten the B flat valve a lot to serve as a GG or FF attachment. This would probably require a second crook to bring the pitch on the valve back to BB flat on the F contra. Or just leave it to pitch the valve in C on the F contra.
It would be desirable to change the triggers on so that the GG or FF valve is on the thumb and the BB flat valve is on the second finger, making it more like other trombones.
It would be very desirable to make the BB flat valve easily revisable, so that the instrument can easily and without tools be changed from playing in CC or BB flat.
A second and easily removable 2nd trigger handle will have to made, to will clear the double tubes of the double slide.
While we are at it the tubes of the D valve could be reversed to face to the rear. This would give space for a longer crook for D flat. This along with shortening the B flat valve would allow the F contra to be played in F/C/D flat, as many players desire. I’m happy with the standard tuning and so won’t do this on mine.
And of course the bell tenon on double slide will have to be changed to match the F bell.
Another project is to improve the double slide, and I believe this will help no matter which bell section is used. It’s long been remarked that the bore on the double slide contra is too small. It’s a triple bore slide with the small tube being about .551, the two middle tubes about .583, and the one large tube being about .610. In addition the slide crooks seem to be matched to the inside of the inner tube and not to the inside of the outer tube like most modern trombones.
Here is a suggestion to improve it using a minimum of new parts. Buy an extra large side inner and outer tube. Throw away the .551 inner and outer tubes. Reconfigure the slide so that it becomes a duo bore of two tubes of .583 and two of .610. Use the lead pipe off of the F contra. (I’ve been using a lead pipe off of an 88H in the .551 pipe, and it plays better with a lead pipe than without) It would be better to replace the slide crooks with ones of bore to match the outer tubes. If new ones cannot be custom made, slide crooks off of the F contra slide could be adapted. Or possibly the crooks for the F contra valve tubing could be used. I’m only suggesting here, as I haven’t had one of the double slides disassembled to be able to measure the bore inside the crooks directly, I’ve had to estimate by measuring the outside diameter and allowing for wall thickness.
Parts need for project (assumes a F contra and a BB flat contra on hand)
Bell section: extra B flat slide crook, maybe a extra D slide crook, fabricate 2nd valve trigger, and parts to reverse valves.
Slide section: extra .610 inner and outer slide, F contra lead pipe, bell tenon to match f bell, and new slide crooks TBD
A different way to accomplish the slide modifications. Buy two F contra slides, cut to length and Siamese them to make a double slide. This might be ok if you don’t already have a double slide contra and can get a supplier to sell you two F contra slides! And you will need an extra slide crook too!
A different way to accomplish the Bell modifications. The F contra bell is modular, i.e. the bell and tuning slide come off with screws. If you already have a double slide contra, you could buy a F contra bell, tuning slide and gooseneck parts, if they will sell them, and use them to replace the same parts on your bell section. You will also need a second valve and tubing.
Any helpful suggestions are welcome.
