Metronome

Metronome
You are encouraged to solve this task according to the task description, using any language you may know.

The task is to implement a metronome. The metronome should be capable of producing high and low audio beats, accompanied by a visual beat indicator, and the beat pattern and tempo should be configurable.

For the purpose of this task, it is acceptable to play sound files for production of the beat notes, and an external player may be used. However, the playing of the sounds should not interfere with the timing of the metronome.

The visual indicator can simply be a blinking red or green area of the screen (depending on whether a high or low beat is being produced), and the metronome can be implemented using a terminal display, or optionally, a graphical display, depending on the language capabilities. If the language has no facility to output sound, then it is permissible for this to implemented using just the visual indicator.

AutoHotkey

Rather basic implementation, but meets the requirements and is reasonably accurate. <lang AHK>bpm = 120 ; Beats per minute pattern = 4/4 ; duration = 100 ; Milliseconds beats = 0  ; internal counter

Gui -Caption

StringSplit, p, pattern, /

Start := A_TickCount

Loop { Gui Color, 0xFF0000 Gui Show, w200 h200 Na SoundBeep 750, duration beats++ Sleep 1000 * 60 / bpm - duration Loop % p1 -1 { Gui Color, 0x00FF00 Gui Show, w200 h200 Na SoundBeep, , duration beats++ Sleep 1000 * 60 / bpm - duration } }

Esc:: MsgBox % "Metronome beeped " beats " beats, over " (A_TickCount-Start)/1000 " seconds. " ExitApp</lang>

C

Using usleep with self correcting delays. Audio is the bell character, which will definitely drive one insane (but I'm ok: my computer doesn't have the bell device). Invoke with ./a.out [beats_per_minute], default to 60. <lang c>#include <stdio.h>

1. include <stdlib.h>
2. include <unistd.h>
3. include <stdint.h>
4. include <signal.h>
5. include <time.h>
6. include <sys/time.h>

struct timeval start, last;

inline int64_t tv_to_u(struct timeval s) { return s.tv_sec * 1000000 + s.tv_usec; }

inline struct timeval u_to_tv(int64_t x) { struct timeval s; s.tv_sec = x / 1000000; s.tv_usec = x % 1000000; return s; }

void draw(int dir, int64_t period, int64_t cur, int64_t next) { int len = 40 * (next - cur) / period; int s, i;

if (len > 20) len = 40 - len; s = 20 + (dir ? len : -len);

printf("\033[H"); for (i = 0; i <= 40; i++) putchar(i == 20 ? '|': i == s ? '#' : '-'); }

void beat(int delay) { struct timeval tv = start; int dir = 0; int64_t d = 0, corr = 0, slp, cur, next = tv_to_u(start) + delay; int64_t draw_interval = 20000; printf("\033[H\033[J"); while (1) { gettimeofday(&tv, 0); slp = next - tv_to_u(tv) - corr; usleep(slp); gettimeofday(&tv, 0);

putchar(7); /* bell */ fflush(stdout);

printf("\033[5;1Hdrift: %d compensate: %d (usec) ", (int)d, (int)corr); dir = !dir;

cur = tv_to_u(tv); d = cur - next; corr = (corr + d) / 2; next += delay;

while (cur + d + draw_interval < next) { usleep(draw_interval); gettimeofday(&tv, 0); cur = tv_to_u(tv); draw(dir, delay, cur, next); fflush(stdout); } } }

int main(int c, char**v) { int bpm;

if (c < 2 || (bpm = atoi(v[1])) <= 0) bpm = 60; if (bpm > 600) { fprintf(stderr, "frequency %d too high\n", bpm); exit(1); }

gettimeofday(&start, 0); last = start; beat(60 * 1000000 / bpm);

return 0; }</lang>

Haskell

Works with: GHC version 7.4.2

<lang Haskell>import Control.Concurrent import Control.Concurrent.MVar import System.Process (runCommand)

-- This program works only on the GHC compiler because of the use of -- threadDelay

data Beep = Stop | Hi | Low

type Pattern = [Beep]

type BeatsPerMinute = Int

minute = 60000000 -- 1 minute = 60,000,000 microseconds

-- give one of the following example patterns to the metronome function

pattern4_4 = [Hi, Low, Low, Low] pattern2_4 = [Hi, Low] pattern3_4 = [Hi, Low, Low] pattern6_8 = [Hi, Low, Low, Low, Low, Low]

-- use this version if you can't play audio, use Windows or don't -- have audio files to play -- beep :: Beep -> IO () -- beep Stop = return () -- beep Hi = putChar 'H' -- beep Low = putChar 'L'

-- use this version if you can and want to play audio on Linux using -- Alsa. Change the name of the files to those of your choice

beep Stop = return () beep Hi = putChar 'H' >> runCommand "aplay hi.wav &> /dev/null" >> return () beep Low = putChar 'L' >> runCommand "aplay low.wav &> /dev/null" >> return ()

tick :: MVar Pattern -> BeatsPerMinute -> IO () tick b i = do

   t <- readMVar b
   case t of
       [Stop] -> return ()
       x -> do
           mapM_ (\v -> forkIO (beep v) >> threadDelay (minute `div` i)) t
           tick b i

metronome :: Pattern -> BeatsPerMinute -> IO () metronome p i = do

   putStrLn "Press any key to stop the metronome."
   b <- newMVar p
   _ <- forkIO $ tick b i
   _ <- getChar
   putMVar b [Stop]</lang>

Liberty BASIC

Requires two supplied wav files for accentuated & standard sounds. <lang lb> WindowWidth =230

   WindowHeight =220

   button #w.b1 "Start",   [start],   LR, 110, 90, 55, 20
   button #w.b2 "Tempo",   [tempo],   LR, 180, 90, 55, 20
   button #w.b3 "Pattern", [pattern], LR,  40, 90, 55, 20

   open "Metronome" for graphics_nsb_nf as #w

   #w "trapclose quit"
   #w "down"
   #w "fill darkblue ; backcolor darkblue ; color white"

   tempo    =   60              '   per minute
   interval =1000 /(tempo /60)  '   timer works in ms
   tickCount =   0              '   cycle counter
   running   =   1              '   flag for state
   bar$      = "HLLL"           '   initially strong-weak-weak-weak
   count     = len( bar$)

   wait

sub quit w$

   close #w$
   end

end sub

[start]

   if running =1 then
       running =0
       #w.b1 "Stop"
       #w.b2 "!disable"
       #w.b3 "!disable"
   else
       running =1
       #w.b1 "Start"
       #w.b2 "!enable"
       #w.b3 "!enable"
   end if
   if running =0 then timer interval, [tick] else timer 0
   wait

[tempo]

   prompt "New tempo 30...360"; tempo$
   tempo =val( tempo$)
   tempo =min( tempo, 360)
   tempo =max( tempo, 30)
   interval =int( 1000 /(tempo /60))
wait

[pattern]

   prompt "New Pattern, eg 'HLLL' "; bar$
   count =len( bar$)
   if count <2 or count >8 then goto [pattern]

wait

[tick]

   'beep and flash
   #w "place 115 40"

   if mid$( bar$, tickCount +1, 1) ="H" then
       playwave "mHi.wav", async
       #w "backcolor blue ; color white ; circlefilled "; 20 -tickCount *2
   else
       playwave "mLo.wav", async
       #w "backcolor cyan ; circlefilled "; 20 -tickCount *2
   end if

   #w "place 50 140 ; backcolor darkblue ; color white"
   #w "\  "; tempo; " beats /min."
   #w "place 85 160"
   #w "\"; bar$

   #w "place 85 120"
   #w "\Beat # "; tickCount +1

   #w "place 115 40"
   #w "color darkblue"

   tickCount =( tickCount +1) mod count

   #w "flush"

   wait</lang>

Perl 6

This code only uses textual output, but any noise-generating commands may be substituted; as long as they are executed synchronously, and do not run longer than the specified duration, the timing loop will compensate, since the sequence operator is determining a list of absolute times for each sleep to target. <lang perl6>sub MAIN ($beats-per-minute = 72, $beats-per-bar = 4) {

   my $duration = 60 / $beats-per-minute;
   my $base-time = now + $duration;
   my $i;

   for $base-time, $base-time + $duration ... * -> $next-time {
       if $i++ %% $beats-per-bar {
           print "\nTICK";
       }
       else {
           print  " tick";
       }
       sleep $next-time - now;
   }

}</lang> Sample run:

$ metronome 120 6

TICK tick tick tick tick tick
TICK tick tick tick tick tick
TICK tick tick tick tick tick
TICK tick tick tick tick tick
TICK tick tick^C

PicoLisp

A short beep (440 Hz, 40 msec) is produced in a child process, while a "pendulum" is swinging left and right. Hitting any key will stop it. <lang PicoLisp>(de metronome (Bpm)

  (if (fork)
     (let Pid @
        (for Pendulum '(" /" . ("^H^H\\ " "^H^H /" .))
           (tell Pid 'call "/usr/bin/beep" "-f" 440 "-l" 40)
           (prin Pendulum)
           (T (key (*/ 30000 Bpm)) (tell Pid 'bye)) )
        (prinl) )
     (wait) ) )</lang>

Test: <lang PicoLisp>: (metronome 60)

/

-> NIL # A key was hit</lang>

PureBasic

Metronome features:

• A periodic graphical-metronomimic image.
• The wav file is included within the resulting executable as raw data.
• A milliseconds between each click field in order to assess accuracy.
• Fine tuning of the click-rate judged via the milliseconds between each click field.
• Volumn controls for when you just can't stand it anymore!

PureBasic output

<lang PureBasic>

Structure METRONOMEs string_mil.i string_err.i string_bmp.i volumn.i window.i image_metronome.i EndStructure

Enumeration

1. STRING_MIL
2. STRING_ERR
3. STRING_BMP
4. BUTTON_ERRM
5. BUTTON_ERRP
6. BUTTON_VOLM
7. BUTTON_VOLP
8. TEXT_MIL
9. TEXT_BMP
10. BUTTON_START
11. BUTTON_STOP
12. WINDOW
13. IMAGE_METRONOME

EndEnumeration

If Not InitSound() MessageRequester("Error", "Sound system is not available", 0) End EndIf

If Not CatchSound(0,?sClick,?eClick-?sClick) MessageRequester("Error", "Could not CatchSound", 0) End EndIf

If LoadFont(0,"tahoma",9,#PB_Font_HighQuality|#PB_Font_Bold) SetGadgetFont(#PB_Default, FontID(0)) EndIf

Procedure.i Metronome(*m.METRONOMEs) Protected j Protected iw =360 Protected ih =360 Protected radius =100 Protected originX =iw/2 Protected originY =ih/2 Protected BeatsPerMinute=*m\string_bmp.i Protected msError.i =*m\string_err.i Protected Milliseconds =int((60*1000)/BeatsPerMinute) Protected msDword.i =Milliseconds*2/12

If CreateImage(*m\image_metronome.i,iw,ih)

Repeat Restore sAngleA

st1=ElapsedMilliseconds() For j=1 to 6 st2=ElapsedMilliseconds() Read.f Angle.f If StartDrawing(ImageOutput(*m\image_metronome.i)) StartTime = ElapsedMilliseconds() Box(0,0,iw,ih,RGB(0,0,0)) CircleX=int(radius*cos(Radian(Angle))) CircleY=int(radius*sin(Radian(Angle))) LineXY(originX,originY, originX+CircleX,originY-CircleY,RGB(255,255,0)) Circle(originX+CircleX,originY-CircleY,10,RGB(255,0,0)) StopDrawing() SetGadgetState(*m\image_metronome.i,ImageID(*m\image_metronome.i)) Endif Delay(msDword-msError) Next While ElapsedMilliseconds()-st1<Milliseconds-msError.i Wend

SetGadgetText(*m\string_mil.i,str(ElapsedMilliseconds()-st1)) PlaySound(0)

st3=ElapsedMilliseconds():err2=0 For j=1 to 6 st4=ElapsedMilliseconds() Read.f Angle.f If StartDrawing(ImageOutput(*m\image_metronome.i))

 StartTime = ElapsedMilliseconds()
 Box(0,0,iw,ih,RGB(0,0,0))
 CircleX=int(radius*cos(Radian(Angle)))
 CircleY=int(radius*sin(Radian(Angle)))
 LineXY(originX,originY, originX+CircleX,originY-CircleY,RGB(255,255,0))
 Circle(originX+CircleX,originY-CircleY,10,RGB(255,0,0))
 StopDrawing()
 SetGadgetState(*m\image_metronome.i,ImageID(*m\image_metronome.i))
 Endif

Delay(msDword-msError) Next While ElapsedMilliseconds()-st3<Milliseconds-msError.i Wend

SetGadgetText(*m\string_mil.i,str(ElapsedMilliseconds()-st3)) PlaySound(0)

ForEver Endif ProcedureReturn i.i EndProcedure

width of image

height of image

allocate memory for our structure

the milliseconds StringGadget number

intial value adjustment for time accuracy [CPU speed]

w =360 h =360

• m.METRONOMEs =Allocatememory(SizeOf(METRONOMEs))
• m\string_mil.i =#STRING_MIL
• m\image_metronome.i =#IMAGE_METRONOME
• m\volumn.i =40

DelayVal =5

draw our initial metronome

radius =100 originX =w/2 originY =h/2 Angle.f =90 If CreateImage(#IMAGE_METRONOME,w,h) If StartDrawing(ImageOutput(#IMAGE_METRONOME)) StartTime = ElapsedMilliseconds() Box(0,0,w,h,RGB(0,0,0)) CircleX=int(radius*cos(Radian(Angle))) CircleY=int(radius*sin(Radian(Angle))) LineXY(originX,originY, originX+CircleX,originY-CircleY,RGB(255,255,0)) Circle(originX+CircleX,originY-CircleY,10,RGB(255,0,0)) StopDrawing() Endif Endif

SoundVolume(0,*m\volumn.i)

window style

style=#PB_Window_SystemMenu style|#PB_Window_Screencentered style|#PB_Window_MinimizeGadget

If Not OpenWindow(#WINDOW,0,0,w+200+12,h+4,"Metronome",style) MessageRequester("Error", "Not OpenWindow", 0) End EndIf

SetWindowColor(#Window,$505050)

metronome

stylet=#PB_Text_Center|#PB_Text_Border

1. TEXT_TUNE=500

data strings

i=2:wp=18:gh=24 i+1:TextGadget(#TEXT_TUNE ,w+wp-10,gh*(i-1),200,gh,"Fine tuning",stylet) i+1 i+1:StringGadget(#STRING_ERR,w+wp+100,gh*(i-1),90,gh,"-5",#PB_String_ReadOnly) i+1 i+1:StringGadget(#STRING_MIL,w+wp+100,gh*(i-1),90,gh,"0",#PB_String_ReadOnly) i+1 i+1:StringGadget(#STRING_BMP,w+wp+100,gh*(i-1),90,gh,"120",#PB_String_Numeric)

control buttons

i=2:wp=10:gh=24 i+1 i+1 i+1:ButtonGadget(#BUTTON_ERRM ,w+wp,gh*(i-1),50,gh,"-") i+0:ButtonGadget(#BUTTON_ERRP ,w+wp+50,gh*(i-1),50,gh,"+") i+1 i+1:TextGadget(#TEXT_MIL ,w+wp,gh*(i-1),100,gh,"MilliSeconds ",stylet) i+1 i+1:TextGadget(#TEXT_BMP ,w+wp,gh*(i-1),100,gh,"BeatsPerMin ",stylet) i+1 i+1:ButtonGadget(#BUTTON_START,w+wp,gh*(i-1),200,gh,"Start",#PB_Button_Toggle) i+1 i+1:ButtonGadget(#BUTTON_VOLM ,w+wp,gh*(i-1),100,gh,"-Volumn") i+0:ButtonGadget(#BUTTON_VOLP ,w+wp+100,gh*(i-1),100,gh,"+Volumn")

the metronome image

stylei=#PB_Image_Border ImageGadget(#IMAGE_METRONOME,0,0,360,360,ImageID(#IMAGE_METRONOME),stylei)

SetGadgetState(#IMAGE_METRONOME,ImageID(#IMAGE_METRONOME))

Repeat ; the control loop for our application

msg= WindowEvent (): Sleep_ (1) wid= EventWindow () mid= EventMenu () gid= EventGadget () etp= EventType () ewp= EventwParam () elp= EventlParam ()

If msg=#PB_Event_CloseWindow  : End : EndIf

If GetAsyncKeyState_(#VK_ESCAPE) : End : EndIf ; remove when app is o.k.

Select msg

case #PB_Event_Gadget

Select gid

 Case #BUTTON_VOLP ; +volumn 
 If *m\volumn.i<100:*m\volumn.i+10
 SoundVolume(0,*m\volumn.i)
 EndIf

Case #BUTTON_VOLM ; -volumn

 If *m\volumn.i>0  :*m\volumn.i-10
 SoundVolume(0,*m\volumn.i)
 EndIf

Case #BUTTON_ERRP ; adjustment for time accuracy [CPU speed]

 DelayVal-1
 *m\string_err.i       =DelayVal
 SetGadgetText(#STRING_ERR,str(0-DelayVal))
 If GetGadgetState(#BUTTON_START)=1
   GoSub Stop
   GoSub Start
   EndIf

Case #BUTTON_ERRM ; adjustment for time accuracy [CPU speed]

 DelayVal+1
 *m\string_err.i       =DelayVal
 SetGadgetText(#STRING_ERR,str(0-DelayVal))
 If GetGadgetState(#BUTTON_START)=1
   GoSub Stop
   GoSub Start
   EndIf

Case #BUTTON_START ; the toggle button for start/stop

 Select GetGadgetState(#BUTTON_START)
 Case 1 :GoSub Stop : GoSub Start   :SetGadgetText(#BUTTON_START,"Stop")
 Case 0 :GoSub Stop                 :SetGadgetText(#BUTTON_START,"Start")
 EndSelect

EndSelect EndSelect ForEver End

Start:  ; start up the thread with new values

• m\string_err.i =DelayVal
• m\string_bmp.i =Val(GetGadgetText(#STRING_BMP))

If *m\string_bmp.i

 MetronomeThread=CreateThread(@Metronome(),*m)
 EndIf

Return

Stop:  ; if the thread is running: stop it If IsThread(MetronomeThread)

 KillThread(MetronomeThread)
 EndIf

Return

DataSection ; an array of angles to be read by: MetronomeThread sAngleA: Data.f 90, 75, 60, 45, 60, 75 ; click Data.f 90,105,120,135,120,105 ; click eAngleA: EndDataSection

DataSection ; a small wav file saved as raw data sClick: Data.a $52,$49,$46,$46,$2E,$08,$00,$00,$57,$41,$56,$45,$66,$6D,$74,$20 Data.a $10,$00,$00,$00,$01,$00,$01,$00,$44,$AC,$00,$00,$44,$AC,$00,$00 Data.a $01,$00,$08,$00,$64,$61,$74,$61,$02,$06,$00,$00,$83,$84,$84,$84 Data.a $85,$85,$86,$86,$88,$89,$8A,$8B,$8E,$91,$95,$9C,$A2,$A9,$B3,$C0 Data.a $CF,$CF,$D0,$CE,$D3,$9B,$47,$31,$31,$33,$32,$32,$32,$32,$33,$32 Data.a $33,$31,$42,$A1,$C9,$C4,$AE,$BD,$D4,$CD,$D1,$CF,$D0,$CF,$CF,$D0 Data.a $CB,$A9,$70,$37,$33,$32,$32,$32,$32,$32,$33,$32,$33,$31,$34,$2E Data.a $53,$AF,$CF,$CF,$CA,$CF,$D0,$CF,$D0,$CF,$D0,$CE,$D3,$AA,$83,$97 Data.a $A1,$8A,$44,$32,$33,$31,$33,$32,$33,$32,$32,$33,$32,$33,$30,$44 Data.a $83,$94,$7E,$7D,$AE,$CF,$D0,$CF,$D0,$CE,$D1,$BF,$B8,$C3,$B9,$B7 Data.a $98,$68,$47,$37,$30,$31,$33,$32,$33,$32,$33,$32,$3D,$49,$48,$3E Data.a $38,$43,$5C,$77,$87,$91,$95,$85,$78,$79,$7A,$80,$8D,$8F,$8A,$89 Data.a $8D,$8D,$88,$81,$83,$89,$7F,$73,$77,$7A,$71,$64,$55,$43,$31,$31 Data.a $34,$32,$34,$3A,$41,$36,$2F,$33,$37,$4D,$5C,$69,$73,$78,$7B,$82 Data.a $8A,$8F,$90,$91,$91,$94,$9B,$9C,$94,$86,$75,$67,$5A,$51,$50,$4D Data.a $45,$42,$41,$41,$43,$48,$51,$54,$59,$65,$75,$82,$87,$86,$83,$7B Data.a $6E,$67,$65,$63,$61,$5F,$5D,$56,$4E,$4B,$50,$57,$5F,$67,$71,$78 Data.a $7B,$7C,$7E,$82,$83,$80,$7C,$79,$76,$71,$6D,$6C,$68,$5E,$52,$4D Data.a $4A,$46,$43,$43,$47,$4B,$4B,$4D,$53,$59,$5D,$65,$6F,$79,$82,$8B Data.a $92,$93,$90,$8B,$88,$83,$7C,$7B,$7B,$76,$6F,$66,$5E,$59,$53,$51 Data.a $53,$55,$57,$59,$5B,$5B,$5A,$5A,$5B,$5E,$61,$67,$6D,$6E,$6C,$69 Data.a $6B,$6F,$72,$73,$75,$77,$79,$78,$79,$7B,$7C,$79,$76,$73,$72,$71 Data.a $6C,$64,$59,$51,$50,$52,$53,$50,$4A,$41,$3B,$3C,$46,$53,$61,$6B Data.a $6E,$6D,$70,$79,$83,$90,$9B,$A0,$9C,$94,$8C,$85,$7E,$7A,$76,$6F Data.a $62,$56,$4E,$48,$45,$48,$4D,$4D,$4C,$4E,$54,$5B,$64,$6F,$79,$80 Data.a $83,$82,$82,$85,$88,$88,$87,$84,$7D,$73,$69,$63,$60,$5D,$5A,$55 Data.a $51,$4E,$4E,$52,$58,$5F,$66,$6A,$6D,$73,$7D,$86,$8B,$8F,$8E,$87 Data.a $81,$80,$7F,$79,$72,$6B,$60,$54,$4D,$4C,$4E,$4E,$4F,$50,$52,$58 Data.a $5F,$67,$6F,$75,$79,$7A,$7B,$7E,$82,$81,$7F,$7C,$75,$6F,$6C,$6B Data.a $6C,$6E,$6F,$6C,$67,$65,$68,$6D,$73,$77,$77,$74,$70,$6C,$6B,$6E Data.a $72,$73,$6F,$67,$60,$5D,$5E,$61,$63,$64,$63,$61,$60,$63,$69,$70 Data.a $76,$79,$79,$7A,$7C,$7F,$81,$81,$80,$7E,$79,$72,$6E,$6B,$67,$65 Data.a $62,$5F,$5D,$5D,$5E,$5F,$62,$65,$6A,$6E,$71,$75,$78,$7B,$7C,$7D Data.a $7E,$7F,$7F,$7E,$7B,$77,$74,$6F,$6A,$67,$63,$5D,$56,$50,$49,$45 Data.a $43,$43,$46,$4B,$50,$55,$5A,$60,$69,$74,$81,$8E,$97,$9D,$9F,$9E Data.a $9C,$9B,$9A,$98,$93,$8A,$7D,$6E,$61,$58,$50,$4C,$49,$46,$45,$44 Data.a $46,$4C,$53,$5C,$66,$6F,$75,$7B,$80,$85,$88,$88,$87,$85,$82,$7E Data.a $7A,$75,$70,$6B,$66,$61,$5D,$5C,$5E,$61,$65,$69,$6B,$6B,$6B,$6A Data.a $6B,$6F,$73,$76,$76,$71,$6B,$64,$61,$62,$67,$6D,$71,$72,$72,$72 Data.a $74,$7A,$81,$85,$88,$87,$85,$82,$80,$7D,$79,$72,$6A,$63,$5F,$5F Data.a $60,$60,$5E,$5A,$58,$58,$5D,$64,$6D,$74,$77,$78,$77,$79,$7D,$82 Data.a 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Tcl

This code only rings the bell on the high beat, which occurs at the start of the bar. <lang tcl>package require Tcl 8.5

lassign $argv bpm bpb if {$argc < 2} {set bpb 4} if {$argc < 1} {set bpm 60}

fconfigure stdout -buffering none set intervalMS [expr {round(60000.0 / $bpm)}] set ctr 0

proc beat {} {

   global intervalMS ctr bpb
   after $intervalMS beat      ;# Reschedule first, to encourage minimal drift
   if {[incr ctr] == 1} {

puts -nonewline "\r\a[string repeat { } [expr {$bpb+4}]]\rTICK"

   } else {

puts -nonewline "\rtick[string repeat . [expr {$ctr-1}]]"

   }
   if {$ctr >= $bpb} {

set ctr 0

   }

}

1. Run the metronome until the user uses Ctrl+C...

beat vwait forever</lang> It might be executed like this: <lang bash>tclsh8.5 metronome.tcl 90 4</lang>