A good place to start is either the key as written in Cosmic Chants, or the key of a monastic recording you like. Both are sound choices.

The keys in Cosmic Chants were chosen to suit the range of the human voice, and in some cases to bring out a unique character of the chant. The piano rendering on the chant page plays the written key.

A monastic recording you like is also a good start. Listen to it, find that key on the harmonium, and learn the chant there.

If the written key or the recording’s key sits well for the group, stay with it.

A comfortable group range is roughly from about middle C (or the B♭ below it) up to about the D or E above the next C. Most of the melody should sit in the middle of that range rather than on the extremes.

A practical check is to look at the highest and lowest notes of the chant, not only the starting note. Try the opening phrase, then the highest phrase, in the key you have chosen. If the top notes feel tight or thin for the group, or the low notes disappear, consider a small move up or down.

Some chants stretch beyond this range, so leaders should be aware of this when they choose a chant. I Am the Sky, for example, notes that it takes some skill to handle the wide vocal range.

If the group or the leader has trouble with the range, or if easier fingerings would help, a modest transposition is fine. Some players prefer C, which uses the white keys. A key you already play often, such as D, can also make a new chant easier to learn.

Keep the move small: ideally a half step or a whole step, and at most two whole steps. The less transposition the better. A large move for the leader’s comfort usually makes it harder for others to sing.

To transpose is to move every note of the melody by the same number of half steps, up or down, so the shape of the tune stays the same. If you move the starting note up a whole step, every later note also moves up a whole step. The intervals do not change. You can think in half steps at the keyboard, or use a neighboring key on the circle of fifths, which is a small change; both are covered in the Key Signatures & Major Scales Guide.

A practical way to choose:

• Find the starting note in the key you began with, then find the highest note of the chant.

• Move the starting note by a half step or a whole step, at most two whole steps, until that high note sits comfortably.

• Play the first phrase and the highest phrase in the new key before you start the chant with the group.

If you read the score, remember that the written notes will no longer match the keys you are playing. It can help to mark the new starting note, or to learn that chant’s melody by interval so you are not tied to the written pitch.

Harmoniums often have two or three sets of reeds. Opening all the stops sounds multiple octaves for one note. A coupler does something similar: it sounds the octave along with the key you are playing. Both are fine to use, and are a matter of the leader’s taste.

A scale-changer (sometimes called a transposer) shifts the keyboard so you can keep the written fingering while the instrument sounds in a different key. It can help when you want to move a chant a little to fit a tambura, or to make it easier to sing, but it also makes the player dependent on that one harmonium. For leading groups, it is better and more flexible to play standard harmoniums, and to transpose with the fingers when a small key change is needed.

Not every harmonium has a scale-changer or a coupler. If you do use a scale-changer, the sounding key is what the singers hear, so check the highest and lowest notes in that sounding key, not only under your fingers. At home, in your own practice, use whatever features of the instrument help you.

Once you have chosen a key, keep it through the chant. Changing key in the middle surprises the group and makes the form harder to follow.

Keep the melody shape the same: the same rises and falls, the same relationship from note to note. Do not flatten a high phrase to avoid a key change, or skip a low note, if a small transposition would let the group sing the line as written.

If you lead more than one chant in a period, each chant can be in its own key. Choose each one for its own range. You do not have to stay in the same key from chant to chant.