In addition to @beefnoguy’s great explanation, I would like to add some finer points.
What @beefnoguy says about wine glasses applies to many, but not all sake.
Just like wine, a sake’s aroma will concentrate in the bulb and allows you to get a more concentrated whiff.
While this amplifies the attributes of many sake, it can result in an over-concentration for some.
Notable exceptions would be:
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Low quality sake The aromas here are simply not ones to be enjoyed (for most people) Aromas from low quality sake tend to be boozy.
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Bold sakes Aromas from bolder sake can stand up for themselves. Many times these are best enjoyed at room temperature or warmed. In this case, a ochoko/guinomi would be the vessel of choice. Think yamahai or kimoto.
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Masu Some, but definitely not all, sake benefit from being drunk from a non-lacquered wooden masu–made from wonderfully fragrant Japanese cedar (sugi). Tarusake is the most obvious choice here. The Japanese cedar taru cask-aged sake is often best enjoyed straight from a Japanese cedar masu. @beefnoguy expounded on tarusake’s virtues a little farther up the thread. Who wouldn’t want to drink this??
- The woody aroma (and to a lesser extent flavor) that is imparted by the Japanese cedar masu can get in the way of more subtle aromatic notes. For this reason, in many cases, it is not a good fit for daiginjo-grade sake.