"Detail" of sounds is high frequency response. When humans are young we can hear as high as 20kHz and CD players and MP3's produce it. FM radio goes to 15kHz and sounds good. But an ordinary AM radio MUST cut the 10kHz interference beat frequency produced by adjacent stations and ordinary interference between them so its frequency response cuts frequencies above about 3kHz. A TRF radio has only a single LC tuned circuit so its frequency response is determined by the bandwidth of the tuned circuit which is affected by using a varactor to replace a mechanically variable capacitor.