The magician is explaining that holding the time value components constant, they will give an answer in line with the required rate of return equal to the market (assuming no issues with credit, liquidity since we’re talking riskless). This is called the yield to maturity. It works well for explaining interest rates to beginners, but it’s full of so many assumptions that it’s pretty useless for putting money on the line. Also, to make this easy to visualize (at least for me), let’s assume we’re talking about annual interest rates, and annual coupons, and full years on the yield curve. With different coupons, or FVs, that means their prices will be different, the PV. Some market participants who are bearish will want premium bonds, the bulls will want discounts (or zeros if you’re Warren Buffet at the turn of the century). But the price issue will figure itself out. That’s all we as market participants can control (unless you’re the Fed and you can set the coupon rate, and even that is done with an auction). Why the par rate? The end goal, I’d say most typically, is to find the implied forward rates, because they show the extra little bit of return you get for lending your money longer. (They also have more complicated uses like bounding the stochastic processes behind a Monte Carlo interest rate forecast, or maybe helping to evaluate the key rate duration of a PAC tranche of an MBS based on forecasted prepayments). Example: If, on a five-year zero-coupon (that’s key) bond, most of the bang for my buck happens in years 1-4, should I limit my loan? The forward curve can help answer this. We do this by using spot rates and finding the pieces between them. The spot rate is just an annual average of all the year-over-year (it could be broken into second-by-second) forward rates that are behind it (remember pricing an FRA? Similar idea of building blocks). Instead of finding the value of my loan going from year 4 to 5, or buying a longer bond, now we’re talking in more basic terms. What’s the value of our 5-year zero in general? Well, it’s the price. And that price shows the average risk of a loan that goes out to the maturity of the zero we’re looking evaluating. Even if a bond has coupons, we can price it if option-free, since we just pretend they’re little zeros. This will be an arbitrage-free price. But it has to be option-free because the optionality could mean that on average the price is correct, but there could be times when the option gets in the way, and all bets are off. Here’s a practical issue, since you seem to like to separate it from theory: we can’t just go into the T-bill or STRIPS market, and pull those YTMs, because these bonds are only either for bulls or people with specific liabilities they’re matching, generally speaking. But we’re not like them typically… Instead, we need to back out the YTMs of coupon bonds, because they’re more representative of the ‘normal’ bond and have better liquidity, etc. As bonds’ prices move to trade at premium or discounts, they become problematic for the same reason zeros are, including other factors now added into the mix, like convexity. To get to said spot curve, bootstrapping is the closed-form (basic) way this is done, and I described this earlier. It would be done with the bid yield of the on-the-run Treasury yield curve, or the ‘par curve.’ (This has some issues in practice, which are way bigger than finding something selling close to par. Problems include the choppiness and noisiness of the bootstrapped implied forward curve, and also the overfitting from so many different maturities. In practice, since we’d wouldn’t be valuing Treasuries this way in all likelihood, we could use Eurodollar futures to construct the short end of our spot curve, and par swap rates for the longer ends, and after inverting the yield curve, interpolate using an instantaneous interest rate. This involves lots of, computers, coffee, patience, and smart people like the magician).