Are you truly that tone deaf that you can't hear the difference between a dull low tone and a more musical mid range tone? You don't need to be able to tell the difference between a middle C and a C# but most of us that can at least enjoy music can hear a difference of an octave. And that's the sort of difference you're looking for. And once you have the spokes set properly to that sort of tone by a shop that knows their stuff you can tap the spokes with a plastic screwdriver handle and get a feel for the tone. Also while you're at it squeeze the spokes together and get a feel for now much they deflect and how spongy or tight they feel. Between the tone and the "elasticity" of the feel of the spokes you should be good if you can remember what they should be like. Obviously to get the spokes set in the first place you'll need to take at least one wheel in and have it tuned up. Then either get the second one done at the same time or use the tone and feel of the one freshly tuned wheel as a guide to tune and true the second wheel.
If you truly can't hear the tones and you don't trust yourself to evaluate and remember the tension from the springiness of the tuned spokes then there's really no alternative. You'll just need to suck it up and take your wheels in from time to time to have them tuned by a good shop. Or else bite the bullet and fork out for a tensionometer. And if you won't be doing such things resonably often it's unlikely that your memory will recall the right feel or the right tone. So again you're stuck with the tensionometer or paying a shop to re-tune your wheels once every few thousand miles.