如何禁用表单中的按钮？

我希望在表单完成时禁用注册按钮。

<form [formGroup]="service.formModelInstrumexts" autocomplete="off" (submit)="onSubmit()"
  style="background-color: #0067b8 !important; margin-top: 25px; margin-left: 600px; margin-right: 600px;">
  <div style="padding: 15px">

<div>
  <h3 style="color: azure">
    اضافه کردن ساز
  </h3>
</div>
    <select   id="ddl" style="width:200px; margin-right: 1%; margin-bottom: 10px; border-radius: 0px;" dir="rtl"
      class="custom-select custom-select-sm">
      <option> لطفا نوع ساز را انتخاب نمایید</option>
      <option *ngFor="let item of type; let i = index" style="color: black;" (click)="test(item.id)" >{{item.name}}
      </option>
    </select>

    <div class="form-group">
      <label>نام</label>
      <input style="width: 40%; margin-left: 60%; border-radius: 0px;" class="form-control" formControlName="Name">
    </div>

    <div class="form-group">
      <label>توضیحات</label>
      <textarea [(ngModel)]="name"  style="direction: rtl; color: rgb(3, 0, 0); border-radius: 0px;" class="form-control" formControlName="Comment"
        aria-label="With textarea"></textarea>
    </div>


    <div  *ngIf="name != null" >
      <app-upload style=" width: 100px; "
        (onUploadFinished)="uploadFinished($event)"></app-upload>
      <img src="http://localhost:54277/{{this.response.dbPath}}" *ngIf="this.response.dbPath != null" width="200px"
        height="200px">
    </div>

    <div class="form-row">
      <div class="form-group col-md-8 offset-md-2">
        <button style="width: 100px; color: #0067b8; background-color: #fff; border-color: transparent; border-radius: 0px;margin-left: 8px;" type="submit" class="btn btn-lg btn-block"
          [disabled]="!service.formModelInstrumexts.valid" >ثبت
        </button>
      </div>
    </div>
  </div>
</form>