OK, I will present a slightly different point of view, but one which IMO chimes with those of Bateman and Hood. We're specifically talking electrolytic caps here. I don't think anyone in the 'Sound Science' forum will disagree that electrolytics do distort, however the remedy for this is not, IMO, to buy some of the exorbitantly priced caps advertised on sale.
1. You don't need 50V capacitors. A cmoy won't have greater than 18V rail-to rail so a 25V cap will be fine, if you're running 9V with a rail splitter, a 16V cap will do. Lower voltage caps are smaller and cheaper.
2. Look at the temperature/time rating of the cap. A 3000 hour / 105°C cap is better than a 2000 hour / 85°C cap, purely in terms of how long it will last, but remember that a cmoy should not be running hot, especially if you don't cram it into a tiny box..
3. Electrolytic caps do cause distortion, this is a measured and measurable effect, but the best way to avoid it is to use an oversize capacitor. So in your case you could use a 3000 hour / 105°C cap (or better hours), rated 16V if you're running 9V with a rail splitter, and use 2200uF instead of 220uF. Because of the lower voltage rating the cap may well be no bigger than the 220uF/50V. The result is a smaller AC voltage across the cap, and consequently smaller distortion. Once the distortion is reduced to levels comparable to that arising from other sources, there is nothing to be gained by spending money to reduce it.
4. With regard to distortion, you only need to concern yourself with caps used for signal coupling (DC blocking) in the signal path. If the cap is bypassing the battery or power supply (opamp power pins), you can be a lot less fussy about the make, and you don't need to make them oversize.
Buy caps with a respectable name, Panasonic, Nippon, Vishay, Rubycon, etc. not 'no-name' caps, but don't spend out for the expensive caps like Black Gate, marketed as 'audio' types. If it says 'audio' on it, it's almost certainly a ripoff.
Many people like to buy high-priced 'audio' caps, as is evidenced by the wide variety on sale, but most engineers and others who trust measured performance parameters feel it is better to save the money and spend it elsewhere.