Sheet music ASCII-art generator

SOGL V0.12, 178 175 174 173 172 171 bytes

l9*6«+@*@¶¹┐∑:@┌ŗ4Ο"γ;]∑«;‽ΗmzΖH+īN D‼,ΨU‛y‚_○¤└yΨšI‘7n2∆╬5;{" -o-”;l3=?Jζ2%Ƨ#bWGk+;}Jz7m««:U+;W7«κArBb3>?Ζo*ŗ}a2\?┌@ŗ}ē9*LI+a╬5b1>?4┐∙b8=?"■QD³‘┼}e9*5+a4-8a>?5+;2-;G↕№}╬5

Try it Here! (θ added for ease of use; To run as 171 bytes it expects the input to be on the stack)

As far as I can tell this works, but if you find any problems, tell me.

Explanation:

first part: canvas creation

l                                get the length of that array
 9*                              multiply by 9
   6«+                           add 12
      @*                         get that many spaces
        @¶                       push a space and a newline
          ¹                      put all the strings on the stack in an array
           ┐∑                    join with vertical bars
             :                   duplicate that string (which is a line with the ending barline but no staff)
              @┌ŗ                replace spaces with dashes (to make it a line with staff)
                 4Ο              encase 4 copies of the space lines in lines with the dashes
                   "...‘         push the G-clef without newlines
                        7n       split into an array of items of length 7
                          2∆╬5   at 1-indexed coordinates [2; -1] place the G-clef in the staff lines, extending the arrays size 
                              ;  get the input split on spaces back on top of the stack

second part: loop, note head placement

{                        loop over the input split on spaces
" -o-”                    push a template for a note head and leger lines
      ;                   get the input optop
       l3=?            }  if the length of the input is 3, then
           J                pop the last letter off from the input
            ζ               get its unicode point
             2%             modulo 2
               Ƨ#bW         get its index in "#b"
                   G        get the template ontop
                    k       remove its 1st letter
                     +      join the replaced input and the template
                      ;     get the input back ontop to be consisntent with how the if started

sidequest: parse the rest of the inputs
J                  pop the last letter off of the remaining input string (the note), leaving the note length as string on the stack below
 z                 push the lowercase alphabet
  7m               get its first 7 letters
    ««             put the first 2 at the end
      :            duplicate it
       U+          append it uppercased to the original
         ;W        get the notes letter ontop and get its 1-indexed index in that just created string
           7«κ     subtract it from 14
              A    save on variable A
               r   convert the note length to a number
                B  save on variable B

b3>?    }          if b>3 (aka if note length is either 4 or 8)
    Ζo*ŗ             replace "o" with "*"
         a2\?   }  if a divides by 2 (aka there isn't staff nor leger lines required)
             ┌@ŗ     replace "-" with " "

ē          push the value of variable E and after that increase it (default is user input number, which errors and defaults to 0)
 9*        multiply by 9
   LI+     increase by 11
      a    push variable a
       ╬5  at those positions (e*9+11, a) insert the note head template in the canvas

third part: flags and stems

b1>?                      if b (note length)>1 (aka if the stem is needed at all)
    4┐∙                   get an array of 4 vertical bars
       b8=?       }       if b==8 (aka if the flag is needed)
           "■QD³‘           push "\    |"
                 ┼          add verically-down-then-horizontally-right

e9*                       push e*9 (now e starts with 1 as it's been increased) (the X coordinate for the flag)
   5+                     add 5 to it
     a4-                  push a-4 (the Y coordinate, 4 less than the note head as arrays get inserted from the top-left corner)
        8a>?         }    if 8>a (aka if the flag needs to be rotated)
            5+              add 5 to the Y coordinate
              ;2-;          subtract 2 from the X coordinate
                  G         get the stem&flag or stem ontop
                   ↕№       reverse it vertically and mirror characters
                      ╬5  insert the array of the stem and maybe flag at those coordinates

JavaScript(ES6), 616 527 bytes

Thanks @shaggy for removing almost 90 bytes

I had no idea about notes... until now, hope I got it right.

f=i=>i.map((v,p)=>(k[e=(w=q+12)*(l="AGFEDCbagfedc".search(v[1]))+p*9+12]="o*"[(s=v[0])>3|0],l<1|l>11&&(k[e-1]=k[e+1]="-"),(t=v[2])&&(k[e-2]="b#"[t>"f"|0]),--s&&[1,2,3,4].map(i=>(k[(b=l<8)?e+w*i-1:e-w*i+1]="|",s>6&&( b?k[e+w*4]="/":k[e-w*4+2]="\\",k[b?e+w*3+1:e-w*3+3]='|')))),k=[...`    /\\  ${s=" ".repeat(q=i.length*9)}  
   | |  ${s}    
---|-|--${l="-".repeat(q)+"|-|"}
   |/   ${t=s+"| |"}
---/|---${l}
  / |   ${t}
-|--|---${l}
 | (| \\ ${t}
-|--|--)${l}
  \\ | / ${t}
-----|--${l}
     |  ${s}   
   *_/  ${s}`])&&k.join``

console.log(f(["8g","8Df","4cs","2C","1A"]))
.as-console-wrapper { max-height: 100% !important; top: 0 }
.as-console-row:after { display: none !important; }

explanation

f=i=>i.map((v,p)=>( // for each note

  k[e=(w=q+12)*(l="AGFEDCbagfedc".search(v[1]))+p*9+12]= // position in 1D array to set the note to
  "o*"[(s=v[0])>3|0], // note value (either o or *)

  l<1|l>11&&(k[e-1]=k[e+1]="-"), // add leger line

  (t=v[2])&&(k[e-2]="b#"[t>"f"|0]), // add sharp or flat

  --s&&[1,2,3,4].map(i=> // add the 4 stem lines
                     (k[(b=l<8)?e+w*i-1:e-w*i+1]="|", // durration over eigth note => add stem

                      s>6&&( // if to add a flag
                        b?k[e+w*4]="/":k[e-w*4+2]="\\", // add flag either on left or the right side

                        k[b?e+w*3+1:e-w*3+3]='|') // add the line after the flag
                     )
                    )
),
// template, extended to the final length with lines
k=[...`    /\\  ${s=" ".repeat(q=i.length*9)}  
   | |  ${s}   
---|-|--${l="-".repeat(q)+"|-|"}
   |/   ${t=s+"| |"}
---/|---${l}
  / |   ${t}
-|--|---${l}
 | (| \\ ${t}
-|--|--)${l}
  \\ | / ${t}
-----|--${l}
     |  ${s}   
   *_/  ${s}`])&&k.join``

Charcoal, 180 171 168 163 bytes

F⁵⁺⸿⸿×-⁺²⁷×⁸№θ ↑⁹←↙↓⁹J⁴¦⁹↑⁶↗¹↑²↖¹↓↙¹↓³↙²↓³ \M²↑(| ↘¹↙)↙¹↓²↙¹↑←_*F⪪θ «A⌕AGFEDCbagfedc§ι¹λJχλA⁺⁹χχ¿⁼³Lι§b#⁼§ι²s→P׳¬﹪λ²→P§o*›ι4¿›ι2¿›λ⁶«↗↑⁴¿›ι8«↘↘¹↓¹»»«↙↓⁴¿›ι8«↗↗¹↑¹

Try it online! Link is to verbose version of code. Explanation:

F⁵⁺⸿⸿×-⁺²⁷×⁸№θ ↑⁹←↙↓⁹

Print the stave.

J⁴¦⁹↑⁶↗¹↑²↖¹↓↙¹↓³↙²↓³ \M²↑(| ↘¹↙)↙¹↓²↙¹↑←_*

Print the clef.

F⪪θ «

Loop through each note.

A⌕AGFEDCbagfedc§ι¹λ

Find the Y-coordinate of the note.

JχλA⁺⁹χχ

This is really sneaky: χ is a variable that is predefined to 10, which is exactly the X-coordinate of the first note's accidental, if it has one. After jumping to that position, 9 is added to it, representing the next note position.

¿⁼³Lι§b#⁼§ι²s→

Print the accidental, if there is one.

P׳¬﹪λ²→P§o*›ι4

Print the ledger lines if necessary and the note. In fact the line is printed on any even y-coordinate although printing it over the stave has no effect of course.

¿›ι2

Nothing more to do for semibreves.

¿›λ⁶«

For notes below the midpoint,

↗↑⁴

draw the stem upwards,

¿›ι8«↘↘¹↓¹

and the flag for quavers.

»»«

For notes above the midpoint,

↙↓⁴

draw the stem downwards,

¿›ι8«↗↗¹↑¹

and the flag for quavers.