| Type predicate | Description | 
|---|
| alist? | association list (list of pairs) | 
| boolean-or-symbol? | boolean or symbol | 
| cheap-list? | list (use this instead of list?for faster processing) | 
| color? | color | 
| exact-rational? | an exact rational number | 
| fraction? | fraction, as pair | 
| grob-list? | list of grobs | 
| index? | non-negative, exact integer | 
| index-or-markup? | index or markup | 
| key? | index or symbol | 
| key-list? | list of indices or symbols | 
| key-list-or-music? | key list or music | 
| key-list-or-symbol? | key list or symbol | 
| ly:skyline-pair? | pair of skylines | 
| markup? | markup | 
| markup-command-list? | markup command list | 
| markup-list? | markup list | 
| moment-pair? | pair of moment objects | 
| musical-length? | non-negative exact rational, fraction (as pair), moment, or +inf.0 | 
| musical-length-as-moment? | non-negative moment with no grace part | 
| musical-length-as-number? | non-negative exact rational or +inf.0 | 
| non-negative-number? | non-negative number | 
| number-list? | number list | 
| number-or-grob? | number or grob | 
| number-or-number-pair? | number or pair of numbers | 
| number-or-pair? | number or pair | 
| number-or-string? | number or string | 
| number-pair? | pair of numbers | 
| number-pair-list? | list of number pairs | 
| positive-fraction? | positive, finite fraction, as pair | 
| positive-musical-length? | positive exact rational, fraction (as pair), moment, or +inf.0 | 
| positive-musical-length-as-moment? | positive moment with no grace part | 
| positive-musical-length-as-number? | positive exact rational or +inf.0 | 
| positive-number? | positive number | 
| rational-or-procedure? | an exact rational or procedure | 
| rhythmic-location? | rhythmic location | 
| sane-simple-time-signature? | simple time signature | 
| sane-time-signature? | time signature | 
| scale? | non-negative rational, fraction, or moment | 
| scheme? | any type | 
| string-or-music? | string or music | 
| string-or-pair? | string or pair | 
| string-or-symbol? | string or symbol | 
| symbol-key-alist? | alist, with symbols as keys | 
| symbol-list? | symbol list | 
| symbol-list-or-music? | symbol list or music | 
| symbol-list-or-symbol? | symbol list or symbol | 
| time-signature? | time signature | 
| void? | void |