As you said, you need to have ISRC in order that the PRO can indentify your track. All the radio-station, TV-station, local-houses, who play music, need to give a list of tracks, which they played. If your track was used: they write down how long they have played it, how many times, etc. and because there are so many tracks called “Time To Run”, or whatever, each track gets an ISRC-code, which should be provided by your publisher, so the PRO know exaclty which track was yours. If you don’t have your own publisher, you need to buy this code yourself. If you check out how much it costs, you actually don’t want to do it yourself, as it costs too much money. So you need to make sure you get a publisher, who is getting these codes for you. Pond5 doesn’t provide it, so you lose potentionally a lot of money, should your music be used in a TV show, trailer, etc. I was researching a lot about this topic, as I didn’t know either where to get these codes, besides being connected to a publisher. Because for example there are tracks, which you don’t want to place in a library, but still want to have this code.
There are two options: You either register ALL your music with one or more publishers, so you get the ISRCs from them, or you publish your music yourself through different providers like CDbaby, DistroKid, etc. if you sell your album there, you get buy these codes there – they will be more affortable. Around 50 cents per track.
Hope that helps
If you still have any questions, I am here to help hopefully