$ fq -i -d mp3 . /test.mp3
mp3> .headers[0].magic | ., tovalue, type, length?
   |00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|0123456789abcdef|
0x0|49 44 33                                       |ID3             |.headers[0].magic: "ID3" (valid)
"ID3"
"string"
3
mp3> .headers[0].magic[0] | ., type, length?
"I"
"string"
1
mp3> .headers[0].magic[-1000] | ., type, length?
""
"string"
0
mp3> .headers[0].magic[1000] | ., type, length?
""
"string"
0
mp3> .headers[0].magic[1:3] | ., type, length?
"D3"
"string"
2
mp3> .headers[0].magic[0:-1] | ., type, length?
"ID"
"string"
2
mp3> .headers[0].magic[-1000:2000] | ., type, length?
"ID3"
"string"
3
mp3> .headers[0].magic["test"] | ., type, length?
error: expected an object but got: string
mp3> [.headers[0].magic[]] | type, length?
error: cannot iterate over: string
mp3> .headers[0].magic | keys
error: keys cannot be applied to: string
mp3> .headers[0].magic | has("a")
error: has cannot be applied to: string
mp3> .headers[0].magic | has(0)
error: has cannot be applied to: string
mp3> .headers[0].magic | type
"string"
mp3> .headers[0].magic | tonumber
error: invalid number: "ID3"
mp3> .headers[0].magic | tostring
"ID3"
mp3> .headers[0].magic + ""
"ID3"
mp3> .headers[0].magic + 1
error: cannot add: string ("ID3") and number (1)
mp3> .headers[0].magic._start | ., type, length?
0
"number"
0
mp3> .headers[0].magic._stop | ., type, length?
24
"number"
24
mp3> .headers[0].magic._len | ., type, length?
24
"number"
24
mp3> .headers[0].magic._name | ., type, length?
"magic"
"string"
5
mp3> .headers[0].magic._sym | ., type, length?
null
"null"
0
mp3> .headers[0].magic._description | ., type, length?
"valid"
"string"
5
mp3> .headers[0].magic._path | ., type, length?
[
  "headers",
  0,
  "magic"
]
"array"
3
mp3> .headers[0].magic._bits | ., type, length?
   |00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|0123456789abcdef|
0x0|49 44 33                                       |ID3             |.: raw bits 0x0-0x2.7 (3)
"buffer"
24
mp3> 
mp3> .headers[0].magic._bytes | ., type, length?
   |00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|0123456789abcdef|
0x0|49 44 33                                       |ID3             |.: raw bits 0x0-0x2.7 (3)
"buffer"
3
mp3> 
mp3> .headers[0].magic._error | ., type, length?
null
"null"
0
mp3> .headers[0].magic._unknown | ., type, length?
false
"boolean"
mp3> .headers[0].magic.a = 1
error: expected an object but got: string
mp3> .headers[0].magic[0] = 1
error: expected an array with index 0 but got: string
mp3> .headers[0].magic.a |= empty
error: expected an object but got: string
mp3> .headers[0].magic[0] |= empty
error: expected an array with index 0 but got: string
mp3> .headers[0].magic | setpath(["a"]; 1)
error: expected an object with key "a" but got: string
mp3> .headers[0].magic | setpath([0]; 1)
error: expected an array with index 0 but got: string
mp3> .headers[0].magic | delpaths([["a"]])
error: expected an object with key "a" but got: string
mp3> .headers[0].magic | delpaths([[0]])
error: expected an array with index 0 but got: string
mp3> ^D