Bass question...

[losthobos]

I've started messing with some longer bass lines from traditional gospel that span the whole octave ..
Ie... 1,3,4,4#, 5,6,b7,7
Question is are all accordion bass reeds laid out the same...seems my highest bass note is Eb and I seem to remember Emilio Allodi telling me that was highest note but may have been chordal rather than bass...
Anyway point is this run seems to work better in some keys than others, .F is particularly smooth, so I'm assuming this is because the notes run up the scale and don't double back an octave at any point...
Hope that makes sense ...any ideas.. @debra
Thanks

 

[debra]

Not all accordions have the same Stradella bass setup.
The lowest note is E on some, F on others, A on many Italian ones, C on a few others...
And with most (but not all) 5 voice bass setups the octave jump changes once or twice (lowest 2 octaves the same, middle octave different, higher 2 octaves again the same but different from the other 3. This helps to hide where the octave jump is when you play "tutti" (all 5 voices playing). Ideally and theoretically you could hide the octave jump completely when you can adjust the volume of each voice according to the "Shepard tone" (check out Shepard tone on Wikipedia for a good explanation).

 

[Siegmund]

A cynic might say "causes 2 problematic octave jumps rather than one," rather than "helps hide the octave jump." It can be surprisingly hard to find out where the jump is, when looking at the specs for an instrument online.

On my Weltmeister, the bottom two sets of reeds run G to F#, the higher reeds E to Eb. This means that at both F#-to-G and Eb-to-E you hear a sudden change in the sound. This can be a real eye-opener when you play something that assumes the octave break is going to happen at C...

When I compose for my own instrument, I tend to want to ensure that 6-7-1 and 4-5-1 bass lines (the two most likely to appear at a 'big finish' moment) will not be interrupted by that leap... the Eb-E break means that in the keys of E,F, and F#, 6-7-1 will be bad and in A or Bb, 4-5 will be bad. The F#-G break means that in the keys of G,Ab, and A, 6-7-1 will be bad and in C or Db, 4-5 will be bad.... leaving only the keys of D and Eb if I want to avoid both. In other keys I pay close attention to which bass register to use.