There are situations where sticking with the default duration may make sense when something looking like (or being) an explicit duration may follow.
Like when switching pitches (or to rest) but not wanting to change the default duration. Like \drums { tamb 4. 8 4 r | 4. 8 4 r } in situations where there _isn't_ something like | to put between r and 4. (here). Since it should act as a shorthand, it should be short to enter. I thought of \drums { tamb 4. 8 4 r0 4. 8 4 r0 } That provides no conflict with the grammar (as the syntax is not affected, just the interpretation). 0 has no extra cost in terms of syntax but seems weird. A superficial look at the ASCII table did not suggest an obvious other choice to me. -- David Kastrup