Is it possible to connect a Thunderbolt 3 adapter into a USB-C port via another adapter?

Exactly what Kappy said.

All Thunderbolt 3 cables have USB-C connectors. Note that this is just the connector itself though it doesn't mean that the rest of the cable is the same.

Ordinary Thunderbolt 3 cables (i.e. cobber-based) also work as USB-C cables. In this manner they are compatible. If you are using an Optical cable, though, it will not work. Try a different adapter or a different TB2 cable. the solution you were given to use a TB2 > TB3 adapter was correct.

You can purchase a TB2 > TB3/USB-C adapter from the apple website

Even though 3rd party companies may provide the compatible cables and adapters, the most optimal equipment to use for Apple products are the ones that Apple sells themselves.

The specifications for the device that the OP is talking about states that the Mac needs a Thunderbolt capable port. No USB-C to Thunderbolt port adapter of any kind is likely to work with that device and a 12" Retina MacBook. And the connectors are not the same.

An adapter will not convert a TB2 output port to TB3. If the adapter you tried did not work then you can either try a different adapter or give up. Akitio makes such an adapter but although I know it works with SSDs I have no way to test it on an audio system. The price isn't too high - about $70. You will find them at Amazon or direct from Akitio They were just acquired by OWC.

They are, however, USB-C 3.1 ports capable of 5Gbps and can be used with TB1 or TB2 or TB3 compatible devices since the connectors are the same. I have several devices connected to that port on a 2016 MacBook and a 2018 MBA. They run faster on the latter than the former. The MBA does support TB3 up to 40Gbps and USB-C 3.1 Gen 2 up to 10Gbps.

That said the 2015 and later MBs have the USB-C 3.1 port that uses the same TB cables. It's easy to think of those as TB ports instead of high speed USB ports.

for both TB2 and TB3 it is possible to get copper-based and optical.

USB-C3.1 ports can read a copper-based signal coming from a TB3 cable but not an optical one which is why I was asking what type of cable you have there.

The 12" Retina MacBook is not Thunderbolt (1, 2, or 3) capable, period, no adapter can make it so.

I have used an Akitio adapter to connect an OWC dock with TB2 ports to the TB3 port of a 2017 iMac. This did work with external USB 3.0 drives. I don't have the Apple adapter to test.

The OP is not talking about using an external USB hard drive. He is talking about using an audio device that requires a Thunderbolt connection.

Is the TB2 cable a copper-based or optical?