The wait might not be too long until you can ask Siri to play music for you on Spotify. The streaming service is beta testing integration with iOS 13's SiriKit audio APIs, which will allow you to ask Siri to interact with the app.
What the API will allow iOS users to do includes everything from playing artists or albums as well as theoretically manage playlists, like tracks, etc. The caveat is you will need to instruct Siri that you want the action done on Spotify, so the virtual assistant knows you want it to interact with this specific app.
You can head over to Spotify's site to try and become a beta tester and test out the feature. Spotify hasn't said when the feature would roll out to all iOS users.
It must also be noted that SiriKit API doesn't support the Apple HomePod so you won't be able to use this with the said device.
This OS-level support has been missing in the past, which Spotify was quick to point out. The company even went to the extent of filing a formal complaint with the European Union. Spotify complained about this restriction and other unfair "competitive advantages" it accused Apple of having for its services.
But it looks like whatever issues Apple and Spotify had is worked out, with the latter quickly moving to adopt the new functionality. Spotify isn't the first out of the gate, though. Pandora, which isn't available in Canada, is the first music app to support the new APIs.
Source: 9to5Mac