Nina, thanks for your reply. I found Bhikkhu Bodhi's note 411 in the
Majjhimanikaya on the meaning of Gandhabba, but I don't have access to
Wijesekera's Buddhist and Vedic Stuties, pp.195-202, which might clarify
it further.

The problem with the term arises from the Mahayana doctrine regarding the
bardo state:

"...when a person dies, there arises a gandharava [so called because they
live on odors] with all five aggreggates, in a mind-made body.

When this bardo being, or gandharva, observes two beings engaged in
intercourse [presuming they are going to take a womb rebirth], they
experience attachment towards the bliss they observe, attracted to the
site of genitals, they mingle with the semen and ovum, and when the zygote
solidifies, the bardo being perishes, and that the stream of conciousness
is now integrated with the newly formed embryo...."

I was hoping to find out that there was a different etymology of the usage
in the two different contexts of "heavenly musician" and "a being destined
for the womb" to clarify why this misunderstanding arose in the Mahayana.

According to the Theravada teaching, there is no such intermediate being
or spirit or bardo realm. Gandhabba means something entirely different to
Gandharva - unfortunately the same Pali word is used in both contexts.