From 宋玉《对楚王问》: when the singer performed elevated tunes "only a handful could join in" — the higher the pitch, the fewer could follow. Originally an image for true connoisseurship, now sometimes a polite way to say "nobody gets it".
mistakes
和 is read hè (harmonize with) and 寡 is guǎ (few). Watch the tones: qǔ gāo hè guǎ.