Hi all. I am looking for a cheap, easy-to-move alternative to my Thompson double bass for solo theory learning (fingering, scales, chords). Would an inexpensive cello work (vs. electric upright which seem pretty expensive)? To find practice time I'm finding I need to move the bass all over the place to get a quiet practice spot. Any input/suggestions appreciated! - Scott
Anything with a different scale won't help you with fingering so you'll have to decide if you're trying to train your hands or your mind. I don't think fingering is a trivial issue but I do think training your mind to hear is more important, if you have to choose one over the other.
For your hands, the Merchant EUB others have recommended seems a great, inexpensive alternative. If for some reason, that doesn't work out, the NS Design full sized EUBs are similar to a DB, at least for scale length. They're missing the back of the neck/body joint, which you can address with a sticky-back piece of wood, and, the full body positioning issues that you have with a 3/4 DB, and, they neither sound nor play that much like a DB, and, you'll probably need some sort of amplification to hear your intonation... but, they're portable, and particularly used, reasonably priced and bowable. If fingering is not your primary concern... I started as a kid on guitar and still have one, and for a year or so, I used it when I had trouble hearing the correct intonation on what I was learning to play. At one point, I also kept a fretted bass guitar around for the same purpose. None of that lasted very long - a few months? These days, I work it out on the DB, or at the piano. I sold my BGs because I don't feel I have the time to learn to play the instrument well, and it's not useful to me as a crutch for my intonation. I still have the guitar I got when I was 9 to transcribe guitar parts.
So, IMO, if your issue is the portability of your DB, a EUB is one possibility, another is to get a portable keyboard like the Yamaha CP. Sounds great, built-in speakers, headphone jack, 2 1/2 octaves. Voice the chords in your left hand and run your scales in your right hand. Chords in the left, solo in the right. Chords in the right, bass lines in the left. It's so powerful because it's all so easily accessible without compromise. And, your piano chops will improve rapidly. Less than 2 years occasional practice for me, it's already my go-to instrument for learning chord progressions.