three-holed flute
籥 centers on a specific ancient wind instrument: a three-holed flute. The meaning is narrow and concrete, referring to this particular musical tool.
籥 combines 竹 (bamboo) with 龠, a pictograph of a panpipe-like instrument. Together they specify a bamboo flute, likely with three holes. The exact historical development is uncertain, but the component relationship is clear.
The top 竹 is bamboo, and the bottom 龠 looks like a row of pipes tied together. Picture a simple bamboo flute with three finger holes, made from a single piece of bamboo.
For ヤク, imagine a yak playing a three-holed flute on a mountain: yak -> ヤク, and the bamboo flute is its instrument.