The reason I suggested the JDS and FY units is the sine wave output is remarkably free of harmonics. Older analog function generators are not as good.
An MCU and an AD9851 board from eBay will get you a good sine wave. But by the time you put it all in a box it will cost as much as the JDS or FY units. Yeah, they have issues, but all are fixable. The price goes up rapidly from there which is the reason that a bunch of old guys are working so hard on the FeelTech. It's got all those lovely BNCs on the back panel and the signal quality is quite good.
For audio work, a good soundcard will be sufficient and for generating clocks almost any MCU dev board will do. There are lots of MCU dev boards with audio codecs that run to 96 KS/S.
Back when I was in grad school and all I had was a 5 MHz recurrent sweep Heathkit scope my signal sources were some oscillators I built on perf board using op amps. There is a denumerably infinite supply of function generator designs available.
If your focus is audio, read "Max Wein, Mr. Hewlett and a Rainy Sunday Afternoon" by Jim Williams. A soundcard and some MATLAB code will let you measure THD to whatever accuracy you desire. In any case you should read the article.
As much as anything, engineering is an attitude and experience. IMHO you should try building a function generator or two before you buy one.