Classical music on demand?

This may be a dumb question but please humor me.  I am now using a Naim Unitiserve as a source and have ripped hundreds of CDs on its hard disc.  As an alternative, is there a way to play (stream) high quality music on demand without ripping CDs?  I listen mostly to classical music so, for example, could I play or stream a Beethoven or Brahms symphony with a choice of conductors and orchestras on my audio system with audio quality equal to or better than CD without having to download anything—similar to watching an on demand program on television?   What software and hardware would I need?   Presumably the hardware would need a screen or would use an iPad or similar screen to select the music. I may be behind the times on such technology so again sorry if my questions show this.  
You might find this article of interest:

You may also want to check Naxos:

And here:

Most classical streaming I’ve encountered is usually programmed music made available through local radio stations or colleges. If you have a university nearby that also has a radio station, you may want to check with them.

Happy Listening and Good Luck with your search
I enjoy but not high resolution. Still, excellent channels. 
You would have to use a computer or other device to purchase a subscription to a streaming service and download the OS. 
Not sure how the Naim Unitiserve works, but it probably will link to the streaming service. Is this device wireless?

Have you ever tried to sync to an internet music station?

Naxos was a good place to download classical. I checked out the link provided above; is their streaming only at 128kbps?
Thanks!  My Naim Unitiserve allows you to rip CDs onto its hard disc and access them with an iPad, phone, etc.  it’s wired to a DAC but can be controlled wirelessly using an app.  It also streams internet radio from all over the world.  I’m looking for something which would let me choose what to hear rather than what’s being played at the moment by a radio station-preferably without having to download anything.  I’m willing to buy any necessary  hardware and to pay for a subscription.  It struck me when I searched for on demand television programs that there should be something similar for audio on demand but I don’t know what it is.  
@fast. You’re on the right track. The music streaming services work like On Demand. There’s Tidal, Spotify, Deezer, Pandora, Apple, etc. You’ve received a couple of recommendations for classical and most services offer a free trial period.
You simply sign up online and load the app to whichever device you are using for your Naim.

Google Primephonic and also Deezer UK for classical. I listen to 90% classical, and I’m also looking for a service that is able to sort thru the  various ways classical is listed.

It seems like you won't have to buy any hardware. 
My advice is to see if your setup works before committing to a subscription. Try and link to one of the internet classical stations and see how well the Naim performs. If it works, then sign up for a free trial of a streaming service.

For western classical music, Primophonic has a very large selection, Tidal HiFi service is CD quality or better but with a slightly smaller selection. Between the two, you'll probably find most if not all your CDs available for streaming on-demand. 
Thanks again for all the sources for streaming classical music. I have another dumb question.  I have a Windows desktop PC in one room and my audio system in another. I use an iPad and iPhone to control my current Naim Unitiserve.  There is no practical way to run a wire from my PC to my audio equipment.  So how do I get the streaming data to my audio system?  Do I need an additional piece of hardware?
I found Primephonic inadequate due to limited catalog.  Quobuz will be here in the fall, supposedly, and then that will be the best High Res Classical Streaming Service.  Tidal is awful for Classical
"So how do I get the streaming data to my audio system? "

Assuming you have WiFi service in your home, the approach to use is stream wirelessly from Bluesound Node2 and connect through either, 1) analog outputs to a preamp/integrated, or 2) digital coax/optical to an external DAC and analog out from DAC to preamp/integrated. Any streamer that supports WiFi will work.