A straight 3ft, 6ft, 10ft, 15ft, even 20ft cables are terrible as antenna, (making them perfect for short runs like instrument to amplification systems) and therefore can be used for your instrument with no worries. and never, ever buy a curly cable - those are deceptively super long and susceptible to become antennas even at moderate lengths. The longer an instrument cable is the better antenna it becomes (That’s where the reputation about noise comes from) - never buy an instrument cable more than 20 feet (unless you need an antenna).
Instrument cables, commonly called “guitar cables”, “signal cable”, unbalanced, TS (Tip-Sleeve) contain two wires one (encased in a covering) to carry the electrons, the second is wrapped around the casing of the first to form the shield.
